net: mdio-gpio: fix device-tree binding documentation

Fix aliases syntax in device-tree binding example to avoid
copy-paste errors (the alias would be dropped silently).
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/mdio-gpio.txt

@@ -14,7 +14,7 @@ node.
 Example:
 
 aliases {
-	mdio-gpio0 = <&mdio0>;
+	mdio-gpio0 = &mdio0;
 };
 
 mdio0: mdio {