arm64: dts: rockchip: Add Radxa ROCK 4D device tree

The Radxa ROCK 4D board is based on the Rockchip rk3576 SoC.

The device tree adds support for basic devices:
 - UART
 - SD Card
 - Ethernet
 - USB
 - RTC

It has 4 USB ports but only 3 are usable as the top left one is used
for maskrom.

It has a USB-C port that is only used for powering the board.

Signed-off-by: Stephen Chen <stephen@radxa.com>
Signed-off-by: Detlev Casanova <detlev.casanova@collabora.com>