bmips: add experimental ethernet support

This adds experimental ethernet support for BCM6318, BCM6328, BCM6362, BCM6368
and BCM63268.
BCM6358 needs a different driver, so there's no support for now.

Working devices:
- Comtrend AR-5315u
- Comtrend AR-5387un
- Comtrend VR-3025u
- Comtrend VR-3032u

Not working devices:
- Netgear DGND3700 v2 (no idea on how the external switch is connected)
- Huawei HG556a ver B (BCM6358 needs a separate driveer)

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

target/linux/bmips/dts/bcm6368-comtrend-vr-3025u.dts

@@ -59,6 +59,12 @@
 	status = "okay";
 };
 
+&ethernet {
+	status = "okay";
+
+	mtd-mac-address = <&cfe 0x6a0>;
+};
+
 &ohci {
 	status = "okay";
 };
@@ -96,6 +102,38 @@
 		     &pinctrl_ephy2_led &pinctrl_ephy3_led>;
 };
 
+&switch0 {
+	ports {
+		port@0 {
+			reg = <0>;
+			label = "lan1";
+
+			phy-handle = <&phy1>;
+		};
+
+		port@1 {
+			reg = <1>;
+			label = "lan2";
+
+			phy-handle = <&phy2>;
+		};
+
+		port@2 {
+			reg = <2>;
+			label = "lan3";
+
+			phy-handle = <&phy3>;
+		};
+
+		port@3 {
+			reg = <3>;
+			label = "lan4";
+
+			phy-handle = <&phy4>;
+		};
+	};
+};
+
 &uart0 {
 	status = "okay";
 };