scsi: qla2xxx: Add heartbeat check

Use "no-op" mailbox command to check if the adapter firmware is still
responsive.

Link: https://lore.kernel.org/r/20210619052427.6440-1-njavali@marvell.com


Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Quinn Tran <qutran@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>