The SCSI cmnd pointer arg would never be NULL, so drop the check. In
addition, its SCSI device pointer would never be NULL.

The only caller is scsi_send_eh_cmnd() -> scsi_abort_eh_cmnd() ->
scsi_try_to_abort_cmd() -> scsi_try_to_abort_cmd(), and in the origin of
that chain those pointers cannot be NULL.
Signed-off-by: John Garry <john.g.garry@oracle.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Link: https://lore.kernel.org/r/20230313093114.1498305-4-john.g.garry@oracle.comSigned-off-by: Martin K. Petersen <martin.petersen@oracle.com>