dt-bindings: display: mediatek: dpi: Add compatible for MediaTek MT8188

For MT8188, the vdosys0 only supports 1T1P mode while the vdosys0 supports
2T1P mode in MT8195. So we need to add dt-binding documentation of dpi for
MediaTek MT8188 SoC.

Signed-off-by: xinlei lee <xinlei.lee@mediatek.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://patchwork.kernel.org/project/linux-mediatek/patch/1666266353-16670-2-git-send-email-xinlei.lee@mediatek.com/


Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>