scsi: qla2xxx: Fix error handling in qlt_alloc_qfull_cmd()

scsi: qla2xxx: Fix error handling in qlt_alloc_qfull_cmd()

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit c04466c17142d5eb566984372b9a5003d1900fe3 ]

The test "if (!cmd)" is not useful because it is guaranteed that cmd !=
NULL.  Instead of testing the cmd pointer, rely on the tag to decide
whether or not command allocation failed.

Cc: Himanshu Madhani <hmadhani@marvell.com>
Cc: Giridhar Malavali <gmalavali@marvell.com>
Fixes: 33e799775593 ("qla2xxx: Add support for QFull throttling and Term Exchange retry") # v3.18.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>