dt-bindings: i2c: Add MediaTek MT7622 i2c binding

Add MT7622 i2c binding to binding file. 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>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-mtk.txt

@@ -7,6 +7,7 @@ Required properties:
       "mediatek,mt2701-i2c", "mediatek,mt6577-i2c": for MediaTek MT2701
       "mediatek,mt6577-i2c": for MediaTek MT6577
       "mediatek,mt6589-i2c": for MediaTek MT6589
+      "mediatek,mt7622-i2c": for MediaTek MT7622
       "mediatek,mt7623-i2c", "mediatek,mt6577-i2c": for MediaTek MT7623
       "mediatek,mt8173-i2c": for MediaTek MT8173
   - reg: physical base address of the controller and dma base, length of memory