scsi: lpfc: Add MDS Diagnostic support.

Added code to support Cisco MDS loopback diagnostic. The diagnostics run
various loopbacks including one which loops-back frame through the
driver.

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