board: rockchip: Add FriendlyElec NanoPi R6C

board: rockchip: Add FriendlyElec NanoPi R6C

The NanoPi R6C is a SBC by FriendlyElec based on the Rockchip RK3588s.
It comes with 4GB or 8GB of RAM, a microSD card slot, optional 32GB eMMC
storage, one M.2 M-Key connector, one RTL8211F 1GbE and one RTL8125
2.5GbE Ethernet port, one USB 2.0 Type-A and one USB 3.0 Type-A port, a
HDMI port, a 30-pin GPIO header as well as multiple buttons and LEDs.

Add initial support for this board using the upstream devicetree sources.

Tested in U-Boot proper:
- Booting from eMMC works
- 1GbE Ethernet works using the eth_eqos driver (tested by ping)
- 2.5GbE Ethernet works using the eth_rtl8169 driver (tested by ping),
  but the status LEDs on this specific port currently aren't working
- NVMe SSD in M.2 socket does get recognized (tested with `nvme scan`
  followed by `nvme details`)

Kernel commit:
d5f1d7437451 ("arm64: dts: rockchip: Add support for NanoPi R6C")

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Sebastian Kropatsch <seb-dev@mail.de>