When flag KASAN is set, we are seeing an following crash while removing
hci_uart module.

[   50.589909] Unable to handle kernel paging request at virtual address 6b6b6b6b6b6b73
[   50.597902] Mem abort info:
[   50.600846]   Exception class = DABT (current EL), IL = 32 bits
[   50.606959]   SET = 0, FnV = 0
[   50.610142]   EA = 0, S1PTW = 0
[   50.613396] Data abort info:
[   50.616401]   ISV = 0, ISS = 0x00000004
[   50.620373]   CM = 0, WnR = 0
[   50.623466] [006b6b6b6b6b6b73] address between user and kernel address ranges
[   50.630818] Internal error: Oops: 96000004 [#1] PREEMPT SMP

[   50.671670] PC is at qca_power_shutdown+0x28/0x100 [hci_uart]
[   50.677593] LR is at qca_close+0x74/0xb0 [hci_uart]
[   50.775689] Process rmmod (pid: 2144, stack limit = 0xffffff801ba90000)
[   50.782493] Call trace:

[   50.872150] [<ffffff8000c3c81c>] qca_power_shutdown+0x28/0x100 [hci_uart]
[   50.879138] [<ffffff8000c3c968>] qca_close+0x74/0xb0 [hci_uart]
[   50.885238] [<ffffff8000c3a71c>] hci_uart_unregister_device+0x44/0x50 [hci_uart]
[   50.892846] [<ffffff8000c3c9f4>] qca_serdev_remove+0x50/0x5c [hci_uart]
[   50.899654] [<ffffff800844f630>] serdev_drv_remove+0x28/0x38
[   50.905489] [<ffffff800850fc44>] device_release_driver_internal+0x140/0x1e4
[   50.912653] [<ffffff800850fd94>] driver_detach+0x78/0x84
[   50.918121] [<ffffff800850edac>] bus_remove_driver+0x80/0xa8
[   50.923942] [<ffffff80085107dc>] driver_unregister+0x4c/0x58
[   50.929768] [<ffffff8000c3ca8c>] qca_deinit+0x24/0x598 [hci_uart]
[   50.936045] [<ffffff8000c3ca10>] hci_uart_exit+0x10/0x48 [hci_uart]
[   50.942495] [<ffffff8008136630>] SyS_delete_module+0x17c/0x224

This crash is due to dereference of hdev, after freeing it.
Signed-off-by: Balakrishna Godavarthi <bgodavar@codeaurora.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>