ARM: dts: rockchip: add veyron-mickey board

Also known as the Asus Chromebit.

Signed-off-by: Chris Zhong <zyw@rock-chips.com>
Tested-by: Caesar Wang <wxt@rock-chips.com>
For the license change:
Acked-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>