phy: Add driver to support individual USB PHYs on sun9i

Unlike previous Allwinner SoCs, there is no central PHY control block
on the A80. Also, OTG support is completely split off into a different
controller.

This adds a new driver to support the regular USB PHYs.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>