ARM: dts: NSP: add MDIO bus controller node

This patch adds the node for the MDIO bus controller, present on the NSP
SoC.
Signed-off-by: Matthew Hagan <mnhagan88@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/boot/dts/bcm-nsp.dtsi

@@ -363,6 +363,13 @@ pwm: pwm@31000 {
 			status = "disabled";
 		};
 
+		mdio: mdio@32000 {
+			compatible = "brcm,iproc-mdio";
+			reg = <0x32000 0x8>;
+			#size-cells = <0>;
+			#address-cells = <1>;
+		};
+
 		rng: rng@33000 {
 			compatible = "brcm,bcm-nsp-rng";
 			reg = <0x33000 0x14>;