ARM: dts: imx25: Remove unneeded keypad properties

Per imx-keypad.yaml, '#address-cells', '#size-cells', 'clock-names'
are not valid properties.

Remove them to fix the following dt-schema warning:

imx25-pdk.dtb: kpp@43fa8000: Unevaluated properties are not allowed ('#address-cells', '#size-cells', 'clock-names' were unexpected)
	from schema $id: http://devicetree.org/schemas/input/imx-keypad.yaml#Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/nxp/imx/imx25.dtsi

@@ -188,12 +188,9 @@ spi1: spi@43fa4000 {
 			};
 
 			kpp: kpp@43fa8000 {
-				#address-cells = <1>;
-				#size-cells = <0>;
 				compatible = "fsl,imx25-kpp", "fsl,imx21-kpp";
 				reg = <0x43fa8000 0x4000>;
 				clocks = <&clks 102>;
-				clock-names = "";
 				interrupts = <24>;
 				status = "disabled";
 			};