dt-bindings: media: Convert MediaTek mt8173-vpu bindings to DT schema

dt-bindings: media: Convert MediaTek mt8173-vpu bindings to DT schema

Convert the existing text-based DT bindings for Mediatek MT8173 Video
Processor Unit to a DT schema.

Signed-off-by: Ariel D'Alessandro <ariel.dalessandro@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
[robh: update MAINTAINERS and mediatek-mdp.txt references]
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>