arm64: dts: rockchip: Add PX30 LVDS

Describe LVDS IP. Add the CRTC and LVDS relevant endpoints so they can
be linked together.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20191224143900.23567-12-miquel.raynal@bootlin.com


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