board: rockchip: add FriendlyElec NanoPi R3S

board: rockchip: add FriendlyElec NanoPi R3S

The NanoPi R3S(as "R3S") is an open source platform with dual-Gbps
Ethernet ports designed and developed by FriendlyElec for IoT
applications.

Specification:
- Rockchip RK3566
- 2GB LPDDR4X RAM
- optional 32GB eMMC module
- SD card slot
- 2x 1000 Base-T
- 3x LEDs (POWER, LAN, WAN)
- 2x Buttons (Reset, MaskROM)
- 1x USB 3.0 Port
- Type-C 5V 2A Power

Signed-off-by: Tianling Shen <cnsztl@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>