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/include/linux/libata.h b/include/linux/libata.h
index 225bfc5..ffd622f 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -772,8 +772,8 @@
 	/*
 	 * Optional features
 	 */
-	int  (*scr_read)(struct ata_port *ap, unsigned int sc_reg, u32 *val);
-	int  (*scr_write)(struct ata_port *ap, unsigned int sc_reg, u32 val);
+	int  (*scr_read)(struct ata_link *link, unsigned int sc_reg, u32 *val);
+	int  (*scr_write)(struct ata_link *link, unsigned int sc_reg, u32 val);
 	void (*pmp_attach)(struct ata_port *ap);
 	void (*pmp_detach)(struct ata_port *ap);
 	int  (*enable_pm)(struct ata_port *ap, enum link_pm policy);