i2c: mediatek: Add i2c compatible for MediaTek MT7622

Add i2c compatible for MT7622. Compare to MT8173 i2c controller,
MT7622 limits message numbers to 255, and does not support 4GB
DMA mode.

Signed-off-by: Jun Gao <jun.gao@mediatek.com>
Reviewed-by: Yingjoe Chen <yingjoe.chen@mediatek.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>