phy: Add Allwinner A64 USB PHY driver

USB PHY implementation for Allwinner SOC's can be handling
in to single driver with different phy configs.

This driver handle all Allwinner USB PHY's start from 4I to
50I(except 9I). Currently added A64 compatibility more will
add in next coming patches.

Current implementation is unable to get pinctrl, clock and reset
details from DT since the dm code on these will add it future.

Driver named as phy-sun4i-usb.c since the same PHY logic
work for all Allwinner SOC's start from 4I to A64 except 9I
with different phy configurations.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Acked-by: Jun Nie <jun.nie@linaro.org>