dt-bindings: arm: mediatek: convert audsys and mt2701-afe-pcm to yaml

Convert the mediatek,audsys binding to YAML, together with the associated
binding bindings/sound/mt2701-afe-pcm.yaml .

Signed-off-by: Eugen Hristev <eugen.hristev@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>