dt-bindings: soc: mediatek: add mtk svs dt-bindings

Document the binding for enabling mtk svs on MediaTek SoC.

Signed-off-by: Roger Lu <roger.lu@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20220516004311.18358-2-roger.lu@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>