sandbox: adc: Add missing header file

Commit: sandbox: add ADC driver

adds the driver without its main header file.
It causes build brake for sandbox_defonfig.

This commit adds a missing header:
- include/sandbox-adc.h

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Minkyu Kang <mk7.kang@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>

include/sandbox-adc.h

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2015 Samsung Electronics
+ * Przemyslaw Marczak <p.marczak@samsung.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef _SANDBOX_ADC_H_
+#define _SANDBOX_ADC_H_
+
+#define SANDBOX_ADC_DEVNAME		"adc@0"
+#define SANDBOX_ADC_DATA_MASK		0xffff /* 16-bits resolution */
+#define SANDBOX_ADC_CHANNELS		4
+#define SANDBOX_ADC_CHANNEL0_DATA	0x0
+#define SANDBOX_ADC_CHANNEL1_DATA	0x1000
+#define SANDBOX_ADC_CHANNEL2_DATA	0x2000
+#define SANDBOX_ADC_CHANNEL3_DATA	0x3000
+
+enum sandbox_adc_mode {
+	SANDBOX_ADC_MODE_SINGLE_CHANNEL = 0,
+	SANDBOX_ADC_MODE_MULTI_CHANNEL,
+};
+
+enum sandbox_adc_status {
+	SANDBOX_ADC_INACTIVE = 0,
+	SANDBOX_ADC_ACTIVE,
+};
+
+#define SANDBOX_ADC_VSS_VALUE		0
+
+#endif