ARM: dts: rockchip: add rockchip RK1108 Evaluation board

RK1108 EVB is designed by Rockchip for CVR field.
This patch add basic support for it, which can boot with
initramfs into shell.

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