Revert "scsi: core: Add scsi_prot_ref_tag() helper"

This reverts commit 294d66c which is
commit 7ba4679 upstream.

As reported, a lot of scsi changes were made just to resolve a 2 line
patch, so let's revert them all and then manually fix up the 2 line
fixup so that things are simpler and potential abi changes are not an
issue.

Link: https://lore.kernel.org/r/ZZ042FejzwMM5vDW@duo.ucw.cz
Reported-by: Pavel Machek <pavel@ucw.cz>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Benjamin Block <bblock@linux.ibm.com>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/scsi/scsi_cmnd.h

@@ -291,13 +291,6 @@ static inline sector_t scsi_get_lba(struct scsi_cmnd *scmd)
 	return blk_rq_pos(scmd->request);
 }
 
-static inline u32 scsi_prot_ref_tag(struct scsi_cmnd *scmd)
-{
-	struct request *rq = blk_mq_rq_from_pdu(scmd);
-
-	return t10_pi_ref_tag(rq);
-}
-
 static inline unsigned int scsi_prot_interval(struct scsi_cmnd *scmd)
 {
 	return scmd->device->sector_size;