dt-bindings: rcar-gen3-phy-usb3: Add bindings for r8a77965

This patch adds bindings for r8a77965 (R-Car M3-N).

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>