dt-bindings: i2c: convert i2c-mt65xx to json-schema

Convert I2C binding for MediaTek SoCs to Devicetree schema.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220407094753.13282-1-angelogioacchino.delregno@collabora.com