gpio: dwapb: correct gpio-cells in binding document

The example uses gpio-cells = 1 while it should be two (it is even
mentioned in the text above).

Cc: [e-mail]
Signed-off-by: Sebastian Andrzej Siewior <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/devicetree/bindings/gpio/snps-dwapb-gpio.txt

···
 	porta: gpio-controller@0 {
 		compatible = "snps,dw-apb-gpio-port";
 		gpio-controller;
-		#gpio-cells = <1>;
+		#gpio-cells = <2>;
 		snps,nr-gpios = <8>;
 		reg = <0>;
 		interrupt-controller;
···
 	portb: gpio-controller@1 {
 		compatible = "snps,dw-apb-gpio-port";
 		gpio-controller;
-		#gpio-cells = <1>;
+		#gpio-cells = <2>;
 		snps,nr-gpios = <8>;
 		reg = <1>;
 	};