scsi: elx: libefc_sli: SLI Descriptors and Queue entries

Continue the libefc_sli SLI-4 library population.

Add SLI-4 Data structures and defines for:

 - Buffer Descriptors (BDEs)

 - Scatter/Gather List elements (SGEs)

 - Queues and their Entry Descriptions for: Event Queues (EQs), Completion
   Queues (CQs), Receive Queues (RQs), and the Mailbox Queue (MQ).

Link: https://lore.kernel.org/r/20210601235512.20104-3-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>