ARM: dts: am437x-gp-evm: Update binding for touchscreen size

Update the bindings for touchscreen size.
Signed-off-by: Roger Quadros <rogerq@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

arch/arm/boot/dts/am437x-gp-evm.dts

@@ -277,8 +277,8 @@ pixcir_ts@5c {
 
 		attb-gpio = <&gpio3 22 GPIO_ACTIVE_HIGH>;
 
-		x-size = <1024>;
-		y-size = <600>;
+		touchscreen-size-x = <1024>;
+		touchscreen-size-y = <600>;
 	};
 };