arm64: dts: rockchip: add initial dts support for Rockpro64

Rockpro64 is a rockchip RK3399 based board from pine64.org.
This patch adds basic device node support for Rockpro64 board and make it able
to bring up.

Peripheral Works
- Sdcard
- USB 2.0, 3.0
- Leds
- Ethernet
- Debug console

Not working:
- USB Type-C

Signed-off-by: Akash Gajjar <Akash_Gajjar@mentor.com>
Acked-by: Deepak Das <Deepak_Das@mentor.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>