arm64: dts: rockchip: Add PX30 DSI DPHY

Add the PHY which outputs MIPI DSI and LVDS.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20191224143900.23567-11-miquel.raynal@bootlin.com


[added dsi power-domain, following vendor-kernel]
Signed-off-by: Heiko Stuebner <heiko@sntech.de>