arm64: dts: mediatek: mt8395-nio-12l: Preconfigure DSI0 pipeline

This board can use a MIPI-DSI panel on the DSI0 connector: in
preparation for adding an overlay for the Radxa Display 8HD,
add a pipeline connecting VDOSYS0 components to DSI0.

This pipeline remains disabled by default, as it is expected
to be enabled only by a devicetree overlay that declares the
actual DSI panel node, completing the graph.

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