[nrf fromtree] tests: adc_accuracy: Add overlay for nrf52840dk.

Add overlay and enable test for nrf52840dk.

Signed-off-by: Bartlomiej Buczek <[email protected]>
(cherry picked from commit dc9a9dc)

Author: nordic-babu

tests/drivers/adc/adc_accuracy_test/boards/nrf52840dk_nrf52840.overlay

@@ -0,0 +1,28 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ */
+
+
+/ {
+	zephyr,user {
+		io-channels = <&adc 0>;
+		reference_mv = <3000>;
+	};
+};
+
+&adc {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,gain = "ADC_GAIN_1_6";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,input-positive = <NRF_SAADC_AIN1>; /* P0.03 */
+		zephyr,resolution = <14>;
+	};
+
+};

tests/drivers/adc/adc_accuracy_test/testcase.yaml

@@ -20,3 +20,4 @@ tests:
       - frdm_kl25z
       - ek_ra8m1
       - frdm_mcxc242
+      - nrf52840dk/nrf52840