arm64: dts: mediatek: mt8188: Add MIPI DSI nodes

Add two MIPI DSI nodes and the associated PHY nodes to support DSI
panels.
Individual board device tree should enable the nodes as needed.

Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://lore.kernel.org/r/20241014111053.2294519-4-fshao@chromium.org


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