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>

drivers/ata/ahci.c

@@ -1052,7 +1052,7 @@ static int ahci_do_softreset(struct ata_port *ap, unsigned int *class,
 
 	DPRINTK("ENTER\n");
 
-	if (ata_port_offline(ap)) {
+	if (ata_link_offline(&ap->link)) {
 		DPRINTK("PHY reports no device\n");
 		*class = ATA_DEV_NONE;
 		return 0;
@@ -1140,7 +1140,7 @@ static int ahci_hardreset(struct ata_port *ap, unsigned int *class,
 
 	ahci_start_engine(ap);
 
-	if (rc == 0 && ata_port_online(ap))
+	if (rc == 0 && ata_link_online(&ap->link))
 		*class = ahci_dev_classify(ap);
 	if (*class == ATA_DEV_UNKNOWN)
 		*class = ATA_DEV_NONE;