linux-phytec-ti

dt: bindings: add bindings for Allwinner A64 usb phy

Update sun4i usb phy dt binding documentation to include support for
Allwinner A64 usb phy.

Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>