iio:dac: Add support for the AD7303

This patch adds support for the AD7303. The AD7303 is a simple 2 channel 8 bit
DAC with an SPI interface.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

include/linux/platform_data/ad7303.h

@@ -0,0 +1,21 @@
+/*
+ * Analog Devices AD7303 DAC driver
+ *
+ * Copyright 2013 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ */
+
+#ifndef __IIO_ADC_AD7303_H__
+#define __IIO_ADC_AD7303_H__
+
+/**
+ * struct ad7303_platform_data - AD7303 platform data
+ * @use_external_ref: If set to true use an external voltage reference connected
+ * to the REF pin, otherwise use the internal reference derived from Vdd.
+ */
+struct ad7303_platform_data {
+	bool use_external_ref;
+};
+
+#endif