rockchip: rk3399: Add support for FriendlyARM NanoPi R4S

rockchip: rk3399: Add support for FriendlyARM NanoPi R4S

This adds support for the NanoPi R4S from FriendlyArm.

Rockchip RK3399 SoC
1GB DDR3 or 4GB LPDDR4 RAM
Gigabit Ethernet (WAN)
Gigabit Ethernet (PCIe) (LAN)
USB 3.0 Port x 2
MicroSD slot
Reset button
WAN - LAN - SYS LED

Co-developed-by: Jensen Huang <jensenhuang@friendlyarm.com>
Signed-off-by: Jensen Huang <jensenhuang@friendlyarm.com>
[minor adjustments]
Co-developed-by: Marty Jones <mj8263788@gmail.com>
Signed-off-by: Marty Jones <mj8263788@gmail.com>
[further adjustments, fixed format issues]
Signed-off-by: Tianling Shen <cnsztl@gmail.com>
Link: https://lore.kernel.org/r/20210319051627.814-2-cnsztl@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>