boards: renesas: Correct reg for ethernet-phy node on ek_ra6m3

Correct reg value for ethernet-phy node on ek_ra6m3 board

Signed-off-by: Khoa Nguyen <khoa.nguyen.xh@renesas.com>

Author: khoa-nguyen-18

boards/renesas/ek_ra6m3/ek_ra6m3.dts

@@ -216,7 +216,7 @@
 	pinctrl-names = "default";
 	status = "okay";
 
-	phy: ethernet-phy@5 {
+	phy: ethernet-phy@0 {
 		compatible = "ethernet-phy";
 		reg = <0>;
 		status = "okay";