arm: dts: mediatek: add ethernet and sgmii dts node for mt7622

This patch add eth and sgmii dts node for mt7622 to support ethernet

Signed-off-by: MarkLee <Mark-MC.Lee@mediatek.com>
diff --git a/arch/arm/dts/mt7622-rfb.dts b/arch/arm/dts/mt7622-rfb.dts
index ec30f5c..f05c3fe 100644
--- a/arch/arm/dts/mt7622-rfb.dts
+++ b/arch/arm/dts/mt7622-rfb.dts
@@ -178,3 +178,16 @@
 	pinctrl-0 = <&watchdog_pins>;
 	status = "okay";
 };
+
+&eth {
+	status = "okay";
+	mediatek,gmac-id = <0>;
+	phy-mode = "sgmii";
+	mediatek,switch = "mt7531";
+	reset-gpios = <&gpio 54 GPIO_ACTIVE_HIGH>;
+
+	fixed-link {
+		speed = <1000>;
+		full-duplex;
+	};
+};