arm64: dts: colibri-imx8x: add parallel RGB support

Add parallel RGB support.

There is currently no support on mainline.

Upstream-Status: Pending
Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>