scsi: elx: libefc_sli: Data structures and defines for mbox commands

Add definitions for SLI-4 mailbox commands and responses.

Link: https://lore.kernel.org/r/20210601235512.20104-4-jsmart2021@gmail.com
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Co-developed-by: Ram Vegesna <ram.vegesna@broadcom.com>
Signed-off-by: Ram Vegesna <ram.vegesna@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>