scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()
In the Linux kernel, the following vulnerability has been resolved:

scsi: ufs: mcq: Add NULL check in ufshcd_mcq_abort()

A race can occur between the MCQ completion path and the abort handler:
once a request completes, __blk_mq_free_request() sets rq->mq_hctx to
NULL, meaning the subsequent ufshcd_mcq_req_to_hwq() call in
ufshcd_mcq_abort() can return a NULL pointer. If this NULL pointer is
dereferenced, the kernel will crash.

Add a NULL check for the returned hwq pointer. If hwq is NULL, log an
error and return FAILED, preventing a potential NULL-pointer
dereference.  As suggested by Bart, the ufshcd_cmd_inflight() check is
removed.

This is similar to the fix in commit 74736103fb41 ("scsi: ufs: core: Fix
ufshcd_abort_one racing issue").

This is found by our static analysis tool KNighter.