[libata] Remove ->port_disable() hook

It was always set to ata_port_disable().  Removed the hook, and replaced
the very few ap->ops->port_disable() callsites with direct calls to
ata_port_disable().

Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/scsi/ipr.c b/drivers/scsi/ipr.c
index 9350fbf..b41dfb5 100644
--- a/drivers/scsi/ipr.c
+++ b/drivers/scsi/ipr.c
@@ -4981,7 +4981,7 @@
 	rc = ipr_device_reset(ioa_cfg, res);
 
 	if (rc) {
-		ap->ops->port_disable(ap);
+		ata_port_disable(ap);
 		goto out_unlock;
 	}
 
@@ -4996,7 +4996,7 @@
 		break;
 	default:
 		ap->link.device[0].class = ATA_DEV_UNKNOWN;
-		ap->ops->port_disable(ap);
+		ata_port_disable(ap);
 		break;
 	};
 
@@ -5262,7 +5262,6 @@
 }
 
 static struct ata_port_operations ipr_sata_ops = {
-	.port_disable = ata_port_disable,
 	.check_status = ipr_ata_check_status,
 	.check_altstatus = ipr_ata_check_altstatus,
 	.dev_select = ata_noop_dev_select,