dsa: fix device tree binding documentation typo on #address-cells

The device tree binding documentation for dsa explicitely states that a
DSA node should have its #address-cells property set to 2, yet the
example still used 1, fix that typo.
Signed-off-by: NFlorian Fainelli <florian@openwrt.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/dsa.txt

@@ -43,7 +43,7 @@ Example:
 
 	dsa@0 {
 		compatible = "marvell,dsa";
-		#address-cells = <1>;
+		#address-cells = <2>;
 		#size-cells = <0>;
 
 		interrupts = <10>;