ata: ahci_platform: Manage SATA PHY

Some platforms have a PHY hooked up to the SATA controller. The PHY
needs to be initialized and powered up for SATA to work. We do that
using the PHY framework.

tj: Minor comment formatting updates.

CC: Balaji T K <balajitk@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tejun <Heo&lt;tj@kernel.org>