phy: sun4i-usb: add support for V3s USB PHY

Allwinner V3s come with a USB PHY controller slightly different to other
SoCs, with only one PHY.

Add support for it.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>