ARM: dts: colibri_vf: Add dcu0 node

Add dumb node for NXP Display Control Unit0(DCU), which permits DM_ENABLED
converted driver to be probed. Currently no display timings are provided
in this node.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Reviewed-by: Oleksandr Suvorov <oleksandr.suvorov@toradex.com>