scsi: ufs: core: Fix device management cmd timeout flow

scsi: ufs: core: Fix device management cmd timeout flow

In the UFS error handling flow, the host will send a device management cmd
(NOP OUT) to the device for link recovery. If this cmd times out and
clearing the doorbell fails, ufshcd_wait_for_dev_cmd() will do nothing and
return. hba->dev_cmd.complete struct is not set to NULL.

When this happens, if cmd has been completed by device, then we will call
complete() in __ufshcd_transfer_req_compl(). Because the complete struct is
allocated on the stack, the following crash will occur:

  ipanic_die+0x24/0x38 [mrdump]
  die+0x344/0x748
  arm64_notify_die+0x44/0x104
  do_debug_exception+0x104/0x1e0
  el1_dbg+0x38/0x54
  el1_sync_handler+0x40/0x88
  el1_sync+0x8c/0x140
  queued_spin_lock_slowpath+0x2e4/0x3c0
  __ufshcd_transfer_req_compl+0x3b0/0x1164
  ufshcd_trc_handler+0x15c/0x308
  ufshcd_host_reset_and_restore+0x54/0x260
  ufshcd_reset_and_restore+0x28c/0x57c
  ufshcd_err_handler+0xeb8/0x1b6c
  process_one_work+0x288/0x964
  worker_thread+0x4bc/0xc7c
  kthread+0x15c/0x264
  ret_from_fork+0x10/0x30

Link: https://lore.kernel.org/r/20221216032532.1280-1-mason.zhang@mediatek.com
Signed-off-by: Mason Zhang <Mason.Zhang@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>