usb: musb: gadget: fix kernel panic if using out ep with FIFO_TXRX style

For shared fifo hw endpoint(with FIFO_TXRX style), only ep_in
field of musb_hw_ep is intialized in musb_g_init_endpoints, and
ep_out is not initialized, but musb_g_rx and rxstate may access
ep_out field of musb_hw_ep by the method below:

	musb_ep = &musb->endpoints[epnum].ep_out

which can cause the kernel panic[1] below, this patch fixes the issue
by getting 'musb_ep' from '&musb->endpoints[epnum].ep_in' for shared fifo
endpoint.

[1], kernel panic
[root@OMAP3EVM /]# musb_interrupt 1583: ** IRQ peripheral usb0008 tx0000 rx4000
musb_stage0_irq 460: <== Power=f0, DevCtl=99, int_usb=0x8
musb_g_rx 772: <== (null), rxcsr 4007 ffffffe8
musb_g_rx 786:  iso overrun on ffffffe8
Unable to handle kernel NULL pointer dereference at virtual address 00000008
pgd = c0004000
[00000008] *pgd=00000000
Internal error: Oops: 17 [#1] PREEMPT
last sysfs file: /sys/devices/platform/musb_hdrc/usb1/usb_device/usbdev1.1/dev
Modules linked in: g_zero
CPU: 0    Tainted: G        W    (2.6.35-rc6-gkh-wl+ #92)
PC is at musb_g_rx+0xfc/0x2ec
LR is at vprintk+0x3f4/0x458
pc : [<c02c07a4>]    lr : [<c006ccb0>]    psr: 20000193
sp : c760bd78  ip : c03c9d70  fp : c760bdbc
r10: 00000000  r9 : fa0ab1e0  r8 : 0000000e
r7 : c7e80158  r6 : ffffffe8  r5 : 00000001  r4 : 00004003
r3 : 00010003  r2 : c760bcd8  r1 : c03cd030  r0 : 0000002e
Flags: nzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: 10c5387d  Table: 8778c019  DAC: 00000017
Process kmemleak (pid: 421, stack limit = 0xc760a2e8)
Stack: (0xc760bd78 to 0xc760c000)
bd60:                                                       ffffffe8 c04b1b58
bd80: ffffffe8 c7c01ac0 00000000 c7e80d24 c0084238 00000001 00000001 c7e80158
bda0: 0000000e 00000008 00000099 000000f0 c760be04 c760bdc0 c02bcd68 c02c06b4
bdc0: 00000099 00000008 00004000 c760bdd8 c03cc4f8 00000000 00000002 c7e80158
bde0: c7d2e300 60000193 c760a000 0000005c 00000000 00000000 c760be24 c760be08
be00: c02bcecc c02bc1ac c7d2e300 c7d2e300 0000005c c760a000 c760be54 c760be28
be20: c00ad698 c02bce6c 00000000 c7d2e300 c067c258 0000005c c067c294 00000001
be40: c760a000 00000000 c760be74 c760be58 c00af984 c00ad5fc 0000005c 00000000
be60: 00000000 00000002 c760be8c c760be78 c0039080 c00af8d0 ffffffff fa200000
be80: c760beec c760be90 c0039b6c c003900c 00000001 00000000 c7d1e240 00000000
bea0: 00000000 c068bae8 00000000 60000013 00000001 00000000 00000000 c760beec
bec0: c0064ecc c760bed8 c00ff7d0 c003a0a8 60000013 ffffffff 00000000 c068bae8
bee0: c760bf24 c760bef0 c00ff7d0 c0064ec4 00000001 00000000 c00ff700 00000000
bf00: c0087f00 00000000 60000013 c0d76a70 c0e23795 00000001 c760bf4c c760bf28
bf20: c00ffdd8 c00ff70c c068bb08 c068bae8 60000013 c0100938 c068bb30 00000000
bf40: c760bf84 c760bf50 c010014c c00ffd84 00000001 00000000 c010000c 00012c00
bf60: c7c33f04 00012c00 c7c33f04 00000000 c0100938 00000000 c760bf9c c760bf88
bf80: c01009a8 c0100018 c760bfa8 c7c33f04 c760bff4 c760bfa0 c0088000 c0100944
bfa0: c760bf98 00000000 00000000 00000001 dead4ead ffffffff ffffffff c08ba2bc
bfc0: 00000000 c049e7fa 00000000 c0087f70 c760bfd0 c760bfd0 c7c33f04 c0087f70
bfe0: c006f5e8 00000013 00000000 c760bff8 c006f5e8 c0087f7c 7f0004ff df2000ff
Backtrace:
[<c02c06a8>] (musb_g_rx+0x0/0x2ec) from [<c02bcd68>] (musb_interrupt+0xbc8/0xcc0)
[<c02bc1a0>] (musb_interrupt+0x0/0xcc0) from [<c02bcecc>] (generic_interrupt+0x6c/0x84)
[<c02bce60>] (generic_interrupt+0x0/0x84) from [<c00ad698>] (handle_IRQ_event+0xa8/0x1ec)
 r7:c760a000 r6:0000005c r5:c7d2e300 r4:c7d2e300
[<c00ad5f0>] (handle_IRQ_event+0x0/0x1ec) from [<c00af984>] (handle_level_irq+0xc0/0x13c)
[<c00af8c4>] (handle_level_irq+0x0/0x13c) from [<c0039080>] (asm_do_IRQ+0x80/0xa0)
 r7:00000002 r6:00000000 r5:00000000 r4:0000005c
[<c0039000>] (asm_do_IRQ+0x0/0xa0) from [<c0039b6c>] (__irq_svc+0x4c/0xb4)
Exception stack(0xc760be90 to 0xc760bed8)
be80:                                     00000001 00000000 c7d1e240 00000000
bea0: 00000000 c068bae8 00000000 60000013 00000001 00000000 00000000 c760beec
bec0: c0064ecc c760bed8 c00ff7d0 c003a0a8 60000013 ffffffff
 r5:fa200000 r4:ffffffff
[<c0064eb8>] (sub_preempt_count+0x0/0x100) from [<c00ff7d0>] (find_and_get_object+0xd0/0x110)
 r5:c068bae8 r4:00000000
[<c00ff700>] (find_and_get_object+0x0/0x110) from [<c00ffdd8>] (scan_block+0x60/0x104)
 r8:00000001 r7:c0e23795 r6:c0d76a70 r5:60000013 r4:00000000
[<c00ffd78>] (scan_block+0x0/0x104) from [<c010014c>] (kmemleak_scan+0x140/0x484)
[<c010000c>] (kmemleak_scan+0x0/0x484) from [<c01009a8>] (kmemleak_scan_thread+0x70/0xcc)
 r8:00000000 r7:c0100938 r6:00000000 r5:c7c33f04 r4:00012c00
[<c0100938>] (kmemleak_scan_thread+0x0/0xcc) from [<c0088000>] (kthread+0x90/0x98)
 r5:c7c33f04 r4:c760bfa8
[<c0087f70>] (kthread+0x0/0x98) from [<c006f5e8>] (do_exit+0x0/0x684)
 r7:00000013 r6:c006f5e8 r5:c0087f70 r4:c7c33f04
Code: e3002312 e58d6000 e2833e16 eb0422d5 (e5963020)
---[ end trace f3d5e96f75c297b7 ]---

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Reviewed-by:   Sergei Shtylyov <sshtylyov@mvista.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Anand Gadiyar <gadiyar@ti.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>