rockchip: add support for FriendlyELEC NanoPi M5

rockchip: add support for FriendlyELEC NanoPi M5

Ethernet LAN port is set to `eth1` (silkscreen "ETH2" and case label "2") next to the 2x USB Type-A
ports and WAN is set to `eth0` (silkscreen "ETH1" and case label "1") next to the USB Type-C port.

The USER ("reset") button serves as the reset button. A short press will reboot and a long press
will reset to factory settings (deleting all data) if using squashfs image.

MASK ("maskrom") and RCRY ("recovery") buttons are enabled but are not set to any specific function

Pressing the POWER button will `poweroff` the device and it will stay off until a power cycle.

Hardware
---------------
* SoC: RockChip RK3576 64-bit ARMv8-A 8 cores big.LITTLE (4x A72 and 4x A53)
* RAM: 3/4GB LPDDR4X or 8/16GB LPDDR5
* Ethernet: 2x GbE (SoC RGMII MAC, RTL8211F PHY)
* 3x LEDs (SYS - red / 1 (WAN) - green / 2 (LAN) - green)
* 4x Buttons (MASK ("maskrom"), RCRY ("recovery"), USER ("reset" - OpenWrt reset), POWER)
* 1x 16MiB SPI NOR on board
* 1x UFS slot for optional UFS 2.0 module (currently not supported)
* 1x microSD card slot (UHS-I)
* 1x HDMI OUT
* 1x Headphone OUT 3.5mm
* 1x M.2 M-key 2280 PCIe slot (PCIe 2.1 x1 supports NVMe SSD)
* 1x M.2 E-key *SDIO* slot for optional RTL8822CS Wi-Fi 5
 * the case has integrated antennae as well as 2x knockouts
 * the device tree is missing the nodes relevant to Wi-Fi operations so it's not supported for now.
* 2x USB 3.2 Gen 1 Type-A Ports
* Power: 1x USB Type-C 6V-20V with both DC and USB PD supported
* Serial: 1500000 8N1 3.3V - 2.54mm 3-pin header next to HDMI

MAC addresses
---------------
WAN (`eth0` case label "1"): generated from /sys/.../mmcblk0/cid (CID of SD card)
LAN (`eth1` case label "2"): WAN + 1

Installation
---------------
Decompress the archive of the OpenWrt sysupgrade image and write it to a microSD card using `dd`
or use Balena Etcher (no need to decompress).

Boot
---------------
Insert microSD card, set boot switch to "UFS/SD" and then supply power.

Signed-off-by: Ryan Leung <untilscour@protonmail.com>
Link: https://github.com/openwrt/openwrt/pull/23008
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>