mmc: dt-bindings: add support for MT7622 SoC

Add the devicetree binding for MT7622 SoC
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/mtk-sd.txt

@@ -12,6 +12,7 @@ Required properties:
 	"mediatek,mt8173-mmc": for mmc host ip compatible with mt8173
 	"mediatek,mt2701-mmc": for mmc host ip compatible with mt2701
 	"mediatek,mt2712-mmc": for mmc host ip compatible with mt2712
+	"mediatek,mt7622-mmc": for MT7622 SoC
 	"mediatek,mt7623-mmc", "mediatek,mt2701-mmc": for MT7623 SoC
 
 - reg: physical base address of the controller and length