scsi: lpfc: Raise config max for lpfc_fcp_mq_threshold variable

Raise the config max for lpfc_fcp_mq_threshold variable to 256.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
CC: Hannes Reinecke <hare@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>