ARM: dts: rockchip: add rockchip PX3 Evaluation board

PX3 EVB is designed by Rockchip for automotive field,
with integrated CVBS (TP2825) / MIPI DSI / LVDS / HDMI
video input/output interface, WIFI/BT/GPS (on a module
named S500 which based on MT6620), Gsensor BMA250E and
light&proximity sensor STK3410.

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