dt-bindings: watchdog: Add compatible for MediaTek MT8188

Add dt-binding documentation of watchdog for MediaTek MT8188 Soc
Signed-off-by: Runyang Chen <runyang.chen@mediatek.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20221026063327.20037-2-Runyang.Chen@mediatek.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

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

@@ -17,6 +17,7 @@ Required properties:
 	"mediatek,mt7986-wdt", "mediatek,mt6589-wdt": for MT7986
 	"mediatek,mt8183-wdt": for MT8183
 	"mediatek,mt8186-wdt", "mediatek,mt6589-wdt": for MT8186
+	"mediatek,mt8188-wdt", "mediatek,mt6589-wdt": for MT8188
 	"mediatek,mt8516-wdt", "mediatek,mt6589-wdt": for MT8516
 	"mediatek,mt8192-wdt": for MT8192
 	"mediatek,mt8195-wdt", "mediatek,mt6589-wdt": for MT8195