samples: drivers: adc: adc_sequence: Update nrf54h20 configuration

Add AIN9 pin in nrf54h20dk to verify AIN8-AIN13 inputs.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>

Author: nordic-krch

samples/drivers/adc/adc_sequence/boards/nrf54h20dk_nrf54h20_cpuapp.overlay

@@ -12,7 +12,7 @@
 
 / {
 	zephyr,user {
-		io-channels = <&adc 0>, <&adc 1>, <&adc 7>;
+		io-channels = <&adc 0>, <&adc 1>, <&adc 2>, <&adc 7>;
 	};
 };
 
@@ -39,6 +39,16 @@
 		zephyr,oversampling = <8>;
 	};
 
+	channel@2 {
+		reg = <2>;
+		zephyr,gain = "ADC_GAIN_1_2";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,input-positive = <NRF_SAADC_AIN9>; /* P9.01 */
+		zephyr,resolution = <12>;
+		zephyr,oversampling = <8>;
+	};
+
 	channel@7 {
 		reg = <7>;
 		zephyr,gain = "ADC_GAIN_1_2";