rockchip: Add support for RK3566 FriendlyElec NanoPi R3S

rockchip: Add support for RK3566 FriendlyElec NanoPi R3S

This commit adds support for the FriendlyElec NanoPi R3S.

CPU: Rockchip RK3566, Quad-core Cortex-A55
RAM: 2GB LPDDR4X
Ethernet: GMAC RTL8211F GbE, PCIe R8111H GbE
USB3.0 Host: Type-A x1
Storage: MicroSD Slot x 1, and optional on-board 32GB eMMC
Debug Serial Port: 3.3V TTL, 3-pin 2.54mm pitch connector, 1500000 bauds
LED: LED x 3
RTC: One low-power RTC, supports backup battery input

Both GbE controllers are working (WAN eth0, LAN eth1).
Appropriate LAN/WAN interface assignments and MAC address generation.
All three LEDs are working.
USB appears to be working and has been tested with mass storage.

Installation - microSD:

-Uncompress the OpenWRT sysupgrade.img.gz
-Write image to microSD card using dd or similar tool

Installation - eMMC:

-Boot from microSD
-Uncompress the OpenWRT sysupgrade.img.gz
-Flash to eMMC : dd if=x.img of=/dev/mmcblk0
-sync
-Remove microSD card
-Reboot

Signed-off-by: Kevin Zhang <kevin@kevinzhang.me>
Link: https://github.com/openwrt/openwrt/pull/16738
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>