ARM i.MX53: mba53: add missing gpio stuff for pca9554

Add properties to make use of pca9554 gpio expander.
Signed-off-by: Markus Niebel <Markus.Niebel@tqs.de>
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx53-mba53.dts

@@ -163,6 +163,8 @@ expander: pca9554@20 {
 		compatible = "pca9554";
 		reg = <0x20>;
 		interrupts = <109>;
+		#gpio-cells = <2>;
+		gpio-controller;
 	};
 
 	sensor2: lm75@49 {