ARM: dts: imx7-mba7: drop incorrect num-chipselects property

This property was never set correctly; it should have been num-cs. As
num-cs support is being removed as well, simply drop it.
Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx7-mba7.dtsi

@@ -179,7 +179,6 @@ &adc2 {
 &ecspi1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_ecspi1>;
-	num-chipselects = <3>;
 	cs-gpios = <&gpio4 0 GPIO_ACTIVE_LOW>, <&gpio4 1 GPIO_ACTIVE_LOW>,
 		   <&gpio4 2 GPIO_ACTIVE_LOW>;
 	status = "okay";
@@ -188,7 +187,6 @@ &ecspi1 {
 &ecspi2 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_ecspi2>;
-	num-chipselects = <1>;
 	status = "okay";
 };