samples: drivers/adc: Support adc example for NXP frdm_mcxa156

Support adc example for NXP frdm_mcxa156

Signed-off-by: Neil Chen <cheng.chen_1@nxp.com>

Author: NeilChen93

samples/drivers/adc/adc_dt/boards/frdm_mcxa156.conf

@@ -0,0 +1 @@
+CONFIG_LPADC_DO_OFFSET_CALIBRATION=y

samples/drivers/adc/adc_dt/boards/frdm_mcxa156.overlay

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+/*
+ * Copyright 2024 NXP
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/dt-bindings/adc/adc.h>
+#include <zephyr/dt-bindings/adc/mcux-lpadc.h>
+
+/ {
+	zephyr,user {
+		/* adjust channel number according to pinmux in board.dts */
+		io-channels = <&lpadc0 0>;
+	};
+};
+
+&lpadc0 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_EXTERNAL0";
+		zephyr,vref-mv = <3300>;
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,resolution = <16>;
+		zephyr,input-positive = <MCUX_LPADC_CH0A>;
+	};
+};