arm64: dts: marvell: add second 1G port on the Armada 8040 DB

Armada 8040 DB is equipped with 4 (2x 10G SFI + 2x 1G RGMII)
ethernet ports of which only one was hitherto enabled.
Because currently mvpp2 driver is capable of supporting only
1G RGMII/SGMII, enable second port from CP slave HW block.
Signed-off-by: NMarcin Wojtas <mw@semihalf.com>
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>

arch/arm64/boot/dts/marvell/armada-8040-db.dts

@@ -169,6 +169,22 @@
 	status = "okay";
 };
 
+&cps_mdio {
+	phy0: ethernet-phy@0 {
+		reg = <0>;
+	};
+};
+
+&cps_ethernet {
+	status = "okay";
+};
+
+&cps_eth1 {
+	status = "okay";
+	phy = <&phy0>;
+	phy-mode = "rgmii-id";
+};
+
 &ap_sdhci0 {
 	status = "okay";
 	bus-width = <4>;