FROMLIST: scsi: ufs: Fix a race condition related to device management commands

If a completion happens after wait_for_completion_timeout() times out
and before ufshcd_clear_cmds() is called then the completion code
may crash on the complete() call in __ufshcd_transfer_req_compl(). This
patch fixes the following crash:

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008
Call trace:
 complete+0x64/0x178
 __ufshcd_transfer_req_compl+0x30c/0x9c0
 ufshcd_poll+0xf0/0x208
 ufshcd_sl_intr+0xb8/0xf0
 ufshcd_intr+0x168/0x2f4
 __handle_irq_event_percpu+0xa0/0x30c
 handle_irq_event+0x84/0x178
 handle_fasteoi_irq+0x150/0x2e8
 __handle_domain_irq+0x114/0x1e4
 gic_handle_irq.31846+0x58/0x300
 el1_irq+0xe4/0x1c0
 efi_header_end+0x110/0x680
 __irq_exit_rcu+0x108/0x124
 __handle_domain_irq+0x118/0x1e4
 gic_handle_irq.31846+0x58/0x300
 el1_irq+0xe4/0x1c0
 cpuidle_enter_state+0x3ac/0x8c4
 do_idle+0x2fc/0x55c
 cpu_startup_entry+0x84/0x90
 kernel_init+0x0/0x310
 start_kernel+0x0/0x608
 start_kernel+0x4ec/0x608

Bug: 238156478
Link: https://lore.kernel.org/linux-scsi/20220713184008.2232094-1-bvanassche@acm.org/T/#u


Change-Id: Icf646e1e536e2d4918e5625574117f6f42e1ff7d
Signed-off-by: Bart Van Assche <bvanassche@google.com>