ARM: dts: Cygnus: Fix MDIO node address/size cells

The MDIO node on Cygnus had an reversed #address-cells and
 #size-cells properties, correct those.

Fixes: 40c26d3a ("ARM: dts: Cygnus: Add the ethernet switch and ethernet PHY")
Reported-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

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

@@ -174,8 +174,8 @@ gpio_crmu: gpio@3024800 {
 		mdio: mdio@18002000 {
 			compatible = "brcm,iproc-mdio";
 			reg = <0x18002000 0x8>;
-			#size-cells = <1>;
-			#address-cells = <0>;
+			#size-cells = <0>;
+			#address-cells = <1>;
 			status = "disabled";
 
 			gphy0: ethernet-phy@0 {