arm64: dts: imx8mm-phyboard-polis-rdk: Remove 'fsl,spi-num-chipselects'

The 'fsl,spi-num-chipselects' property is not a valid one, so remove it.
Signed-off-by: Fabio Estevam <festevam@denx.de>
Reviewed-by: Yannic Moog <y.moog@phytec.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm-phyboard-polis-rdk.dts

@@ -143,7 +143,6 @@ can0: can@0 {
 /* TPM */
 &ecspi2 {
 	cs-gpios = <&gpio5 13 GPIO_ACTIVE_LOW>;
-	fsl,spi-num-chipselects = <1>;
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_ecspi2>;
 	#address-cells = <1>;