dt-bindings: display: mediatek: disp: add documentation for MT8167 SoC

Add binding documentation for the MT8167 SoC

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>