ARM: dts: imx53-ppd: Remove 'num-chipselects' property

The 'num-chipselects' property is not a valid property according
to Documentation/devicetree/bindings/spi/fsl-imx-cspi.txt, so
let's remove it.
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

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

@@ -319,7 +319,6 @@ gpioxra1: gpio@3 {
 &ecspi2 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_ecspi2>;
-	num-chipselects = <1>;
 	cs-gpios = <&gpio2 26 GPIO_ACTIVE_LOW>;
 	status = "okay";