dt-bindings: i2c: modify information formats

Use common name MediaTek and modify the compatible information
formats of all SoCs to the same.

Signed-off-by: Jun Gao <jun.gao@mediatek.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>