dt-bindings: fix example of allwinner interrupt controller

The documented value of #interrupt-cells is 1.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/interrupt-controller/allwinner,sun4i-ic.txt

@@ -14,5 +14,5 @@ intc: interrupt-controller {
 	compatible = "allwinner,sun4i-ic";
 	reg = <0x01c20400 0x400>;
 	interrupt-controller;
-	#interrupt-cells = <2>;
+	#interrupt-cells = <1>;
 };