arm64: dts: rockchip: Enable USB 2.0 ports on Radxa E20C

arm64: dts: rockchip: Enable USB 2.0 ports on Radxa E20C

The Radxa E20C has one USB2.0 Type-A HOST port and one USB2.0 Type-C port.

The Type-C port is conneced to a FE1.1s_QFN USB hub on the board, with its
ports being connected to the XHCI usb controller and an usb-uart bridge.

This also means, the XHCI controller can only be used in device-mode.

Add support for using the USB 2.0 ports on Radxa E20C.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
[set xhci to peripheral and add comment about the outward-facing hub]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20260529190355.4148175-3-heiko@sntech.de