ARM: dts: imx6q-kontron-samx6i: Remove old fsl,spi-num-chipselects

The property "fsl,spi-num-chipselects" is gone since commit 790739c4
("dt-bindings: spi: Convert imx cspi to json-schema").
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx6q-kontron-samx6i.dtsi

@@ -14,7 +14,6 @@ / {
 
 /* Quad/Dual SoMs have 3 chip-select signals */
 &ecspi4 {
-	fsl,spi-num-chipselects = <3>;
 	cs-gpios = <&gpio3 24 GPIO_ACTIVE_LOW>,
 		   <&gpio3 29 GPIO_ACTIVE_LOW>,
 		   <&gpio3 25 GPIO_ACTIVE_LOW>;