ARM: dts: rockchip: add rk3188 lcd controller nodes

Add the core display subsystem and vop nodes to rk3188.
Vop0 has a fully dedicated set of pins and only vop1 needs to
do pinctrl to have display output, so also add the necessary
pinctrl entries for it.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by Sandy Huang <hjc@rock-chips.com>