mwifiex: debugfs: Fix out of bounds array access

When reading the contents of '/sys/kernel/debug/mwifiex/p2p0/info',
the following panic occurs:

$ cat /sys/kernel/debug/mwifiex/p2p0/info
Unable to handle kernel paging request at virtual address 74706164
pgd = de530000
[74706164] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
Modules linked in: phy_twl4030_usb omap2430 musb_hdrc mwifiex_sdio mwifiex
CPU: 0 PID: 1635 Comm: cat Not tainted 3.10.0-rc1-00010-g1268390 #1
task: de16b6c0 ti: de048000 task.ti: de048000
PC is at strnlen+0xc/0x4c
LR is at string+0x3c/0xf8
pc : [<c02c123c>]    lr : [<c02c2d1c>]    psr: a0000013
sp : de049e10  ip : c06efba0  fp : de6d2092
r10: bf01a260  r9 : ffffffff  r8 : 74706164
r7 : 0000ffff  r6 : ffffffff  r5 : de6d209c  r4 : 00000000
r3 : ff0a0004  r2 : 74706164  r1 : ffffffff  r0 : 74706164
Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 10c5387d  Table: 9e530019  DAC: 00000015
Process cat (pid: 1635, stack limit = 0xde048240)
Stack: (0xde049e10 to 0xde04a000)
9e00:                                     de6d2092 00000002 bf01a25e de6d209c
9e20: de049e80 c02c438c 0000000a ff0a0004 ffffffff 00000000 00000000 de049e48
9e40: 00000000 2192df6d ff0a0004 ffffffff 00000000 de6d2092 de049ef8 bef3cc00
9e60: de6b0000 dc358000 de6d2000 00000000 00000003 c02c45a4 bf01790c bf01a254
9e80: 74706164 bf018698 00000000 de59c3c0 de048000 de049f80 00001000 bef3cc00
9ea0: 00000008 00000000 00000000 00000000 00000000 00000000 00000000 00000000
9ec0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
9ee0: 00000000 00000000 00000000 00000001 00000000 00000000 6669776d 20786569
9f00: 20302e31 2e343128 392e3636 3231702e 00202933 00000000 00000003 c0294898
9f20: 00000000 00000000 00000000 00000000 de59c3c0 c0107c04 de554000 de59c3c0
9f40: 00001000 bef3cc00 de049f80 bef3cc00 de049f80 00000000 00000003 c0108a00
9f60: de048000 de59c3c0 00000000 00000000 de59c3c0 00001000 bef3cc00 c0108b60
9f80: 00000000 00000000 00001000 bef3cc00 00000003 00000003 c0014128 de048000
9fa0: 00000000 c0013f80 00001000 bef3cc00 00000003 bef3cc00 00001000 00000000
9fc0: 00001000 bef3cc00 00000003 00000003 00000001 00000001 00000001 00000003
9fe0: 00000000 bef3cbdc 00011984 b6f1127c 60000010 00000003 18dbdd2c 7f7bfffd
[<c02c123c>] (strnlen+0xc/0x4c) from [<c02c2d1c>] (string+0x3c/0xf8)
[<c02c2d1c>] (string+0x3c/0xf8) from [<c02c438c>] (vsnprintf+0x1e8/0x3e8)
[<c02c438c>] (vsnprintf+0x1e8/0x3e8) from [<c02c45a4>] (sprintf+0x18/0x24)
[<c02c45a4>] (sprintf+0x18/0x24) from [<bf01790c>] (mwifiex_info_read+0xfc/0x3e8 [mwifiex])
[<bf01790c>] (mwifiex_info_read+0xfc/0x3e8 [mwifiex]) from [<c0108a00>] (vfs_read+0xb0/0x144)
[<c0108a00>] (vfs_read+0xb0/0x144) from [<c0108b60>] (SyS_read+0x44/0x70)
[<c0108b60>] (SyS_read+0x44/0x70) from [<c0013f80>] (ret_fast_syscall+0x0/0x30)
Code: e12fff1e e3510000 e1a02000 0a00000d (e5d03000)
---[ end trace ca98273dc605a04f ]---

The panic is caused by the mwifiex_info_read() routine assuming that
there can only be four modes (0-3) which is an invalid assumption.
For example, when testing P2P, the mode is '8' (P2P_CLIENT) so the
code accesses data beyond the bounds of the bss_modes[] array which
causes the panic.  Fix this by updating bss_modes[] to support the
current list of modes and adding a check to prevent the out-of-bounds
access from occuring in the future when more modes are added.

Signed-off-by: Mark A. Greer <mgreer@animalcreek.com>
Acked-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>