arm: dts: mediatek: enable sgmii mode and mt7531 switch for mt7629

This patch enable sgmii mode and mt7531 switch support in mt7629
ethernet dts node

Signed-off-by: MarkLee <Mark-MC.Lee@mediatek.com>

arch/arm/dts/mt7629-rfb.dts

@@ -24,12 +24,14 @@
 
 &eth {
 	status = "okay";
-	mediatek,gmac-id = <1>;
-	phy-mode = "gmii";
-	phy-handle = <&phy0>;
-
-	phy0: ethernet-phy@0 {
-		reg = <0>;
+	mediatek,gmac-id = <0>;
+	phy-mode = "sgmii";
+	mediatek,switch = "mt7531";
+	reset-gpios = <&gpio 28 GPIO_ACTIVE_HIGH>;
+
+	fixed-link {
+		speed = <1000>;
+		full-duplex;
 	};
 };