ARM: dts: rockchip: Add RK3288 VOP gamma LUT address

RK3288 SoC VOPs have optional support Gamma LUT setting,
which requires specifying the Gamma LUT address in the devicetree.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20191010194351.17940-4-ezequiel@collabora.com


Signed-off-by: Heiko Stuebner <heiko@sntech.de>