Bluetooth: btusb: mediatek: Fix kernel crash when releasing mtk iso interface

Bluetooth: btusb: mediatek: Fix kernel crash when releasing mtk iso interface

When performing reset tests and encountering abnormal card drop issues
that lead to a kernel crash, it is necessary to perform a null check
before releasing resources to avoid attempting to release a null pointer.

<4>[   29.158070] Hardware name: Google Quigon sku196612/196613 board (DT)
<4>[   29.158076] Workqueue: hci0 hci_cmd_sync_work [bluetooth]
<4>[   29.158154] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
<4>[   29.158162] pc : klist_remove+0x90/0x158
<4>[   29.158174] lr : klist_remove+0x88/0x158
<4>[   29.158180] sp : ffffffc0846b3c00
<4>[   29.158185] pmr_save: 000000e0
<4>[   29.158188] x29: ffffffc0846b3c30 x28: ffffff80cd31f880 x27: ffffff80c1bdc058
<4>[   29.158199] x26: dead000000000100 x25: ffffffdbdc624ea3 x24: ffffff80c1bdc4c0
<4>[   29.158209] x23: ffffffdbdc62a3e6 x22: ffffff80c6c07000 x21: ffffffdbdc829290
<4>[   29.158219] x20: 0000000000000000 x19: ffffff80cd3e0648 x18: 000000031ec97781
<4>[   29.158229] x17: ffffff80c1bdc4a8 x16: ffffffdc10576548 x15: ffffff80c1180428
<4>[   29.158238] x14: 0000000000000000 x13: 000000000000e380 x12: 0000000000000018
<4>[   29.158248] x11: ffffff80c2a7fd10 x10: 0000000000000000 x9 : 0000000100000000
<4>[   29.158257] x8 : 0000000000000000 x7 : 7f7f7f7f7f7f7f7f x6 : 2d7223ff6364626d
<4>[   29.158266] x5 : 0000008000000000 x4 : 0000000000000020 x3 : 2e7325006465636e
<4>[   29.158275] x2 : ffffffdc11afeff8 x1 : 0000000000000000 x0 : ffffffdc11be4d0c
<4>[   29.158285] Call trace:
<4>[   29.158290]  klist_remove+0x90/0x158
<4>[   29.158298]  device_release_driver_internal+0x20c/0x268
<4>[   29.158308]  device_release_driver+0x1c/0x30
<4>[   29.158316]  usb_driver_release_interface+0x70/0x88
<4>[   29.158325]  btusb_mtk_release_iso_intf+0x68/0xd8 [btusb (HASH:e8b6 5)]
<4>[   29.158347]  btusb_mtk_reset+0x5c/0x480 [btusb (HASH:e8b6 5)]
<4>[   29.158361]  hci_cmd_sync_work+0x10c/0x188 [bluetooth (HASH:a4fa 6)]
<4>[   29.158430]  process_scheduled_works+0x258/0x4e8
<4>[   29.158441]  worker_thread+0x300/0x428
<4>[   29.158448]  kthread+0x108/0x1d0
<4>[   29.158455]  ret_from_fork+0x10/0x20
<0>[   29.158467] Code: 91343000 940139d1 f9400268 927ff914 (f9401297)
<4>[   29.158474] ---[ end trace 0000000000000000 ]---
<0>[   29.167129] Kernel panic - not syncing: Oops: Fatal exception
<2>[   29.167144] SMP: stopping secondary CPUs
<4>[   29.167158] ------------[ cut here ]------------

Fixes: ceac1cb0259d ("Bluetooth: btusb: mediatek: add ISO data transmission functions")
Signed-off-by: Chris Lu <chris.lu@mediatek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>