arm64: dts: imx8-ss-dma: add io-channel-cells to adc nodes

This commit adds io-channel-cells property to the ADC nodes. This
property is required in order for an IIO consumer driver to work.
Especially required for Apalis iMX8 QM, as the touchscreen driver
uses ADC channels with the ADC driver based on IIO framework.
Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Acked-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8-ss-dma.dtsi

@@ -270,6 +270,7 @@ i2c3: i2c@5a830000 {
 
 	adc0: adc@5a880000 {
 		compatible = "nxp,imx8qxp-adc";
+		#io-channel-cells = <1>;
 		reg = <0x5a880000 0x10000>;
 		interrupts = <GIC_SPI 240 IRQ_TYPE_LEVEL_HIGH>;
 		interrupt-parent = <&gic>;
@@ -284,6 +285,7 @@ adc0: adc@5a880000 {
 
 	adc1: adc@5a890000 {
 		compatible = "nxp,imx8qxp-adc";
+		#io-channel-cells = <1>;
 		reg = <0x5a890000 0x10000>;
 		interrupts = <GIC_SPI 241 IRQ_TYPE_LEVEL_HIGH>;
 		interrupt-parent = <&gic>;