ARM: dts: rockchip: add dts for ChipSPARK Rayeager PX2 board

This add support for Rayeager PX2, Rockchip PX2 based development board
made by ChipSPARK.

Signed-off-by: FUKAUMI Naoki <naobsd@gmail.com>
Tested-by: Andy Yan <andy.yan@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>