usb: g_audio: Fix crash at driver removal

usb: g_audio: Fix crash at driver removal

If g_audio fails to open the sound control device, it crashes at removal:

Insertion:
[ 4143.836536] g_audio gadget: unable to open sound control device file: /dev/snd/controlC0
[ 4143.836543] g_audio gadget: we need at least one control device
[ 4143.836551] g_audio gadget: Linux USB Audio Gadget, version: Dec 18, 2008
[ 4143.836558] g_audio gadget: g_audio ready

Removal:
[ 4146.802643] BUG: unable to handle kernel paging request at 00023018
[ 4146.802655] IP: [<c10af9f5>] filp_close+0xa/0x5b
[ 4146.802674] *pdpt = 0000000015426001 *pde = 0000000000000000
[ 4146.802684] Oops: 0000 [#1] PREEMPT SMP
[ 4146.802692] last sysfs file: /sys/power/state
[ 4146.802701] Modules linked in: g_audio(-) ioh_udc fuse asix usbnet [last unloaded: g_audio]
[ 4146.802719]
[ 4146.802728] Pid: 1394, comm: rmmod Not tainted 2.6.33.5-26.1-ivi #1 To be filled by O.E.M./To be filled by O.E.M.
[ 4146.802738] EIP: 0060:[<c10af9f5>] EFLAGS: 00010206 CPU: 0
[ 4146.802746] EIP is at filp_close+0xa/0x5b
[ 4146.802753] EAX: 00023000 EBX: 00023000 ECX: 00000046 EDX: df842680
[ 4146.802760] ESI: e071cd4c EDI: df842680 EBP: ddbbbef0 ESP: ddbbbee4
[ 4146.802768]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
[ 4146.802776] Process rmmod (pid: 1394, ti=ddbba000 task=dd95a4f0 task.ti=ddbba000)
[ 4146.802782] Stack:
[ 4146.802787]  d540c280 e071cd4c df2bc000 ddbbbefc e071b82c df11e440 ddbbbf04 e071c622
[ 4146.802804] <0> ddbbbf28 e071c47f 00000008 e071cd74 df11e464 df2bc01c df2bc000 e071ce68
[ 4146.802822] <0> 00000880 ddbbbf38 e07fd1b8 e071cef0 00000000 ddbbbf40 e071b9f4 ddbbbf48
[ 4146.802842] Call Trace:
[ 4146.802857]  [<e071b82c>] ? gaudio_cleanup+0x87/0xe0 [g_audio]
[ 4146.802869]  [<e071c622>] ? audio_unbind+0x8/0xc [g_audio]
[ 4146.802881]  [<e071c47f>] ? composite_unbind+0x8d/0xcb [g_audio]
[ 4146.802895]  [<e07fd1b8>] ? usb_gadget_unregister_driver+0x7b/0xc0 [ioh_udc]
[ 4146.802908]  [<e071b9f4>] ? usb_composite_unregister+0x15/0x17 [g_audio]
[ 4146.802920]  [<e071c633>] ? cleanup+0xd/0xf [g_audio]
[ 4146.802932]  [<c105a938>] ? sys_delete_module+0x185/0x1dd
[ 4146.802944]  [<c101c3ea>] ? do_page_fault+0x248/0x276
[ 4146.802956]  [<c10027d0>] ? sysenter_do_call+0x12/0x26
[ 4146.802962] Code: 12 5f 3a 00 8b 43 04 8b 40 0c 0f b3 30 3b 73 44 73 03 89 73 44 89 f8 e8 f1 61 3a 00 5b 5e 5f 5d c3 55 89 e5 57 89 d7 56 53 89 c3 <8b> 40 18 85 c0 75 0f 68 32 15 5e c1 31 f6 e8 52 39 3a 00 5a eb
[ 4146.803058] EIP: [<c10af9f5>] filp_close+0xa/0x5b SS:ESP 0068:ddbbbee4
[ 4146.803071] CR2: 0000000000023018
[ 4146.803112] ---[ end trace 0989a7e023da0434 ]---

This patch makes sure not to assign the_card if gaudio_open_snd_dev fails,
since the parent function will deallocate the card.

Also make sure all filp's in gaudio_open_snd_dev is assigned NULL upon error
and gaudio_close_snd_dev only cleanups when the filp's are non-NULL.

Signed-off-by: Richard Röjfors <richard.rojfors@pelagicore.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>