samples: drivers: adc: Add xmc45_relax_kit overlay

Adds xmc45_relax_kit overlay to run the sample.

Signed-off-by: Andriy Gelman <[email protected]>

Author: talih0

samples/drivers/adc/boards/xmc45_relax_kit.overlay

@@ -0,0 +1,27 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright (c) 2022 Andriy Gelman <[email protected]>
+ */
+
+#include <zephyr/dt-bindings/adc/adc.h>
+
+/ {
+	zephyr,user {
+		io-channels = <&adc0 0>; /* P14.0 */
+	};
+};
+
+&adc0 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	channel@0 {
+		reg = <0>;
+		zephyr,acquisition-time = <ADC_ACQ_TIME_DEFAULT>;
+		zephyr,gain = "ADC_GAIN_1";
+		zephyr,reference = "ADC_REF_INTERNAL";
+		zephyr,resolution = <12>;
+	};
+	status = "okay";
+};