arm64: dts: rockchip: add usb2-phy otg-port support for rk3399

Add otg-port nodes for both u2phy0 and u2phy1. The otg-port can
be used for USB2.0 part of USB3.0 OTG controller.

Signed-off-by: William Wu <wulf@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>