PHY: sunxi: Add driver for sunxi usb phy

The Allwinner A1x / A2x SoCs have 2 or 3 usb phys which are all accessed
through a single set of registers. Besides this there are also some other
phy related bits which need poking, which are per phy, but shared between the
ohci and ehci controllers, so these are also controlled from this new phy
driver.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>