ARM: dts: rockchip: add core rk3288-veyron backlight and panel nodes

Many Veyron chromebooks share the same panel type, so define the core
settings for all of them and allow the few runaways to override it later.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Douglas Anderson <dianders@chromium.org>