scsi: target: core: Add RTPI field to target port

SAM-5 4.6.5.2 (Relative Port Identifier attribute) defines the attribute as
unique across SCSI target ports.

The change introduces RTPI attribute to se_portal group. The value is
unique across all enabled SCSI target ports. It also limits number of SCSI
target ports to 65535.

Signed-off-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Link: https://lore.kernel.org/r/20230301084512.21956-2-d.bogdanov@yadro.com


Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>