ARM: dts: rockchip: Add VMARC RK3288 SOM initial support

VMARC RK3288 SOM is a standard SMARC SOM design with
Rockchip RK3288 SoC, which is designed by Vamrs.

Specification:
- Rockchip RK3288
- PMIC: RK808
- SD slot, 16GiB eMMC
- 2xUSB-2.0, 1xUSB3.0
- USB-C for power supply
- Ethernet, PCIe
- HDMI, MIPI-DSI/CSI, eDP

Add initial support for VMARC RK3288 SOM, this would use
with associated carrier board.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>