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/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
index 48ee8c7..e187298 100644
--- a/drivers/scsi/libsas/sas_ata.c
+++ b/drivers/scsi/libsas/sas_ata.c
@@ -294,10 +294,10 @@
 	}
 }
 
-static int sas_ata_scr_write(struct ata_port *ap, unsigned int sc_reg_in,
+static int sas_ata_scr_write(struct ata_link *link, unsigned int sc_reg_in,
 			      u32 val)
 {
-	struct domain_device *dev = ap->private_data;
+	struct domain_device *dev = link->ap->private_data;
 
 	SAS_DPRINTK("STUB %s\n", __func__);
 	switch (sc_reg_in) {
@@ -319,10 +319,10 @@
 	return 0;
 }
 
-static int sas_ata_scr_read(struct ata_port *ap, unsigned int sc_reg_in,
+static int sas_ata_scr_read(struct ata_link *link, unsigned int sc_reg_in,
 			    u32 *val)
 {
-	struct domain_device *dev = ap->private_data;
+	struct domain_device *dev = link->ap->private_data;
 
 	SAS_DPRINTK("STUB %s\n", __func__);
 	switch (sc_reg_in) {