libata-link: linkify PHY-related functions

Make the following PHY-related functions to deal with ata_link instead
of ata_port.

* sata_print_link_status()
* sata_down_spd_limit()
* ata_set_sata_spd_limit() and friends
* sata_link_debounce/resume()
* sata_scr_valid/read/write/write_flush()
* ata_link_on/offline()

This patch introduces no behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
index 564cd23..700843a 100644
--- a/drivers/ata/libata.h
+++ b/drivers/ata/libata.h
@@ -78,8 +78,8 @@
 extern int ata_dev_reread_id(struct ata_device *dev, unsigned int readid_flags);
 extern int ata_dev_revalidate(struct ata_device *dev, unsigned int readid_flags);
 extern int ata_dev_configure(struct ata_device *dev);
-extern int sata_down_spd_limit(struct ata_port *ap);
-extern int sata_set_spd_needed(struct ata_port *ap);
+extern int sata_down_spd_limit(struct ata_link *link);
+extern int sata_set_spd_needed(struct ata_link *link);
 extern int ata_down_xfermask_limit(struct ata_device *dev, unsigned int sel);
 extern int ata_set_mode(struct ata_port *ap, struct ata_device **r_failed_dev);
 extern void ata_sg_clean(struct ata_queued_cmd *qc);