arm64: dts: mediatek: mt8188: Add DP-INTF nodes

Add the primary and secondary dp-intf nodes.
These DP-INTF hardware IPs are the sink of the vdosys0 and vdosys1
display pipelines for the internal and external displays, respectively.

Individual board device tree should enable the nodes and connect input
and output ports as needed.

Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://lore.kernel.org/r/20241014111053.2294519-9-fshao@chromium.org


Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>