ARM: dts: Enable Ethernet on STi's B2120 boards

These boards are mounted with Realtek RTL8367 switch.
We consider the bootloader will have intiliazed the switch before jumping into
the kernel, so we declare it as a fixed link.
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>

arch/arm/boot/dts/stih407-b2120.dts

@@ -25,6 +25,7 @@ memory {
 
 	aliases {
 		ttyAS0 = &sbc_serial0;
+		ethernet0 = &ethernet0;
 	};
 
 };

arch/arm/boot/dts/stih410-b2120.dts

@@ -25,6 +25,7 @@ memory {
 
 	aliases {
 		ttyAS0 = &sbc_serial0;
+		ethernet0 = &ethernet0;
 	};
 
 	soc {

arch/arm/boot/dts/stihxxx-b2120.dtsi

@@ -87,5 +87,11 @@ st_dwc3: dwc3@8f94000 {
 			status = "okay";
 		};
 
+		ethernet0: dwmac@9630000 {
+			st,tx-retime-src = "clkgen";
+			status = "okay";
+			phy-mode = "rgmii";
+			fixed-link = <0 1 1000 0 0>;
+		};
 	};
 };