scsi: elx: efct: RQ buffer, memory pool allocation and deallocation APIs

Add driver definitions for:

 - RQ data buffer allocation and deallocate.

 - Memory pool allocation and deallocation APIs.

 - Mailbox command submission and completion routines.

Link: https://lore.kernel.org/r/20210601235512.20104-21-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>