dt-bindings: net: mdio: Add address and size cells

MDIO controllers should have child nodes with a singe value in their reg
properties being the ID of the PHY in the bus.

Let's add the proper constraints on #address-cells and #size-cells.
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/net/mdio.yaml

@@ -21,6 +21,12 @@ properties:
   $nodename:
     pattern: "^mdio(@.*)?"
 
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
   reset-gpios:
     maxItems: 1
     description: