staging: usbip: stub: update refcounts for devices and interfaces

The stub driver expects to access the usb interface
and usb device structures even if the device has been
disconnected in the meantime.

This change gets a reference to them in the stub probe
function using usb_get_intf()/usb_get_dev() and drops them
in the disconnect function.

This fixes an oops observed with a Logic Controls Line
display (0fa8:a030) which disconnects itself when it is
reset:

[ 1348.562274] BUG: unable to handle kernel paging request at 5f7433e5
[ 1348.562327] IP: [<c0393b02>] usb_lock_device_for_reset+0x22/0xd0
[ 1348.562374] *pde = 00000000
[ 1348.562397] Oops: 0000 [#1]
[ 1348.562418] last sysfs file: /sys/devices/pci0000:00/0000:00:10.2/usb4/4-1/bConfigurationValue
[ 1348.562454] Modules linked in: usbip vhci_hcd usbip_common_mod fbcon tileblit font bitblit softcursor serio_raw uvesafb pcspkr via_rng snd_via82xx gameport snd_ac97_codec ac97_bus snd_pcm_oss snd_mixer_oss snd_pcm snd_page_alloc snd_mpu401_uart snd_rawmidi snd_seq_oss snd_seq_midi_event snd_seq snd_timer snd_seq_device snd usbhid hid via_rhine soundcore mii igel_flash aufs pata_via
[ 1348.562649]
[ 1348.562670] Pid: 2855, comm: usbip_eh Not tainted (2.6.32 #23.37-ud-r113) M300C
[ 1348.562704] EIP: 0060:[<c0393b02>] EFLAGS: 00010216 CPU: 0
[ 1348.562734] EIP is at usb_lock_device_for_reset+0x22/0xd0
[ 1348.562762] EAX: 5f7433cd EBX: 5f7433cd ECX: de293a5c EDX: dd326a00
[ 1348.562793] ESI: 5f7433cd EDI: 000400f6 EBP: cf43ff48 ESP: cf43ff38
[ 1348.562824]  DS: 007b ES: 007b FS: 0000 GS: 00e0 SS: 0068
[ 1348.562854] Process usbip_eh (pid: 2855, ti=cf43e000 task=d2c7f230 task.ti=cf43e000)
[ 1348.562884] Stack:
[ 1348.562900]  d6ec9960 de2939cc 5f7433cd 5f743431 cf43ff70 df8fd32f de2939cc d2c7f230
[ 1348.562940] <0> cf43ff70 00000282 00000282 de2939cc d2c7f230 d2c7f230 cf43ffa8 df84416d
[ 1348.562987] <0> cf43ff88 d2c7f230 de293a24 d2c7f230 00000000 d2c7f230 c014e760 cf43ff94
[ 1348.563042] Call Trace:
[ 1348.563073]  [<df8fd32f>] ? stub_device_reset+0x3f/0x110 [usbip]
[ 1348.563114]  [<df84416d>] ? event_handler_loop+0xcd/0xe8 [usbip_common_mod]
[ 1348.563156]  [<c014e760>] ? autoremove_wake_function+0x0/0x50
[ 1348.563193]  [<df843d80>] ? usbip_thread+0x0/0x60 [usbip_common_mod]
[ 1348.563230]  [<df843dd1>] ? usbip_thread+0x51/0x60 [usbip_common_mod]
[ 1348.563265]  [<c014e374>] ? kthread+0x74/0x80
[ 1348.563294]  [<c014e300>] ? kthread+0x0/0x80
[ 1348.563326]  [<c0103c47>] ? kernel_thread_helper+0x7/0x10
[ 1348.563351] Code: 00 e8 73 4d 00 00 5d c3 90 55 89 e5 83 ec 10 89 5d f4 89 75 f8 89 7d fc 0f 1f 44 00 00 8b 3d c0 2e 67 c0 81 c7 fa 00 00 00 89 c3 <8b> 40 18 89 d6 85 c0 75 15 b8 ed ff ff ff 8b 5d f4 8b 75 f8 8b
[ 1348.563528] EIP: [<c0393b02>] usb_lock_device_for_reset+0x22/0xd0 SS:ESP 0068:cf43ff38
[ 1348.563570] CR2: 000000005f7433e5
[ 1348.563593] ---[ end trace 9c3f1e3a2e5299d9 ]---

Signed-off-by: Max Vozeler <max@vozeler.com>
Tested-by: Mark Wehby <MWehby@luxotticaRetail.com>
Tested-by: Steven Harms <sharms@luxotticaRetail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>