ARM: dts: imx28-evk: Enable touchscreen support

Provide 'lradc-touchscreen-wires' property to the LRADC driver, so that
touchscreen can be functional.

Signed-off-by: Fabio Estevam <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx28-evk.dts

···
 			};
 
 			lradc@80050000 {
+				fsl,lradc-touchscreen-wires = <4>;
 				status = "okay";
 			};