libata: make SCR access ops per-link

Logically, SCR access ops should take @link; however, there was no
compelling reason to convert all SCR access ops when adding @link
abstraction as there's one-to-one mapping between a port and a non-PMP
link.  However, that assumption won't hold anymore with the scheduled
addition of slave link.

Make SCR access ops per-link.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index 79e3a8e..825461a 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4868,10 +4868,8 @@
 int sata_scr_read(struct ata_link *link, int reg, u32 *val)
 {
 	if (ata_is_host_link(link)) {
-		struct ata_port *ap = link->ap;
-
 		if (sata_scr_valid(link))
-			return ap->ops->scr_read(ap, reg, val);
+			return link->ap->ops->scr_read(link, reg, val);
 		return -EOPNOTSUPP;
 	}
 
@@ -4897,10 +4895,8 @@
 int sata_scr_write(struct ata_link *link, int reg, u32 val)
 {
 	if (ata_is_host_link(link)) {
-		struct ata_port *ap = link->ap;
-
 		if (sata_scr_valid(link))
-			return ap->ops->scr_write(ap, reg, val);
+			return link->ap->ops->scr_write(link, reg, val);
 		return -EOPNOTSUPP;
 	}
 
@@ -4925,13 +4921,12 @@
 int sata_scr_write_flush(struct ata_link *link, int reg, u32 val)
 {
 	if (ata_is_host_link(link)) {
-		struct ata_port *ap = link->ap;
 		int rc;
 
 		if (sata_scr_valid(link)) {
-			rc = ap->ops->scr_write(ap, reg, val);
+			rc = link->ap->ops->scr_write(link, reg, val);
 			if (rc == 0)
-				rc = ap->ops->scr_read(ap, reg, &val);
+				rc = link->ap->ops->scr_read(link, reg, &val);
 			return rc;
 		}
 		return -EOPNOTSUPP;