scsi: qla2xxx: Add host attribute to trigger MPI hang

Add a mechanism to trigger MPI pause for debugging purposes.

Link: https://lore.kernel.org/r/20210810043720.1137-2-njavali@marvell.com


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