ARM: dtsi: axp22x: add node for ADC

This adds a DT node for the ADC of the PMIC so that there can be
consumers of its IIO channels declaring their consumptions via DT.

Signed-off-by: Quentin Schulz <[e-mail]>
Acked-by: Chen-Yu Tsai <[e-mail]>
Signed-off-by: Maxime Ripard <[e-mail]>

arch/arm/boot/dts/axp22x.dtsi

···
 		status = "disabled";
 	};
 
+	axp_adc: adc {
+		compatible = "x-powers,axp221-adc";
+		#io-channel-cells = <1>;
+	};
+
 	battery_power_supply: battery-power-supply {
 		compatible = "x-powers,axp221-battery-power-supply";
 		status = "disabled";