sd: Fix discard granularity when LBPRZ=1

Commit 397737223c ("sd: Make discard granularity match logical block
size when LBPRZ=1") accidentally set the granularity to one byte instead
of one logical block on devices that provide deterministic zeroes after
UNMAP.

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reported-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Fixes: 397737223c
Cc: <stable@vger.kernel.org> #v4.4+

drivers/scsi/sd.c

@@ -648,7 +648,7 @@ static void sd_config_discard(struct scsi_disk *sdkp, unsigned int mode)
 	 */
 	if (sdkp->lbprz) {
 		q->limits.discard_alignment = 0;
-		q->limits.discard_granularity = 1;
+		q->limits.discard_granularity = logical_block_size;
 	} else {
 		q->limits.discard_alignment = sdkp->unmap_alignment *
 			logical_block_size;