ARM: mediatek: dts: Add MT6797 binding

This patch adds the binding for the MT6797 SoC.
Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/watchdog/mtk-wdt.txt

@@ -5,6 +5,7 @@ Required properties:
 - compatible should contain:
 	"mediatek,mt2701-wdt", "mediatek,mt6589-wdt": for MT2701
 	"mediatek,mt6589-wdt": for MT6589
+	"mediatek,mt6797-wdt", "mediatek,mt6589-wdt": for MT6797
 
 - reg : Specifies base physical address and size of the registers.