scsi: elx: libefc_sli: SLI-4 register offsets and field definitions

This is the initial patch for the new Emulex target mode SCSI driver.

 - Create the new Emulex source level directory drivers/scsi/elx and add
   the directory to the MAINTAINERS file.

 - Create the first library subdirectory drivers/scsi/elx/libefc_sli.  This
   library is a SLI-4 interface library.

 - Start the population of the libefc_sli library with definitions of SLI-4
   hardware register offsets and definitions.

Link: https://lore.kernel.org/r/20210601235512.20104-2-jsmart2021@gmail.com
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Daniel Wagner <dwagner@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>