[PATCH] libata: add dev->ap

Add dev->ap which points back to the port the device belongs to.  This
makes it unnecessary to pass @ap for silly reasons (e.g. printks).
Also, this change is necessary to accomodate later PM support which
will introduce ATA link inbetween port and device.

Signed-off-by: Tejun Heo <htejun@gmail.com>

include/linux/libata.h

@@ -358,6 +358,7 @@ struct ata_host_stats {
 };
 
 struct ata_device {
+	struct ata_port		*ap;
 	u64			n_sectors;	/* size of device, if ATA */
 	unsigned long		flags;		/* ATA_DFLAG_xxx */
 	unsigned int		class;		/* ATA_DEV_xxx */