iio: add ad5761 DAC driver

ad5761 is a 1-channel DAC with configurable output range.
The driver uses the regulator interface for its voltage ref.

It shares its register layout with ad5761r, ad5721 and ad5721r.

Differences:
ad5761* are 16 bit, ad5721* are 12 bits.
ad57*1r have an internal reference.

Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 5263c51..5dc7150 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -111,6 +111,16 @@
 	  To compile this driver as a module, choose M here: the
 	  module will be called ad5755.
 
+config AD5761
+	tristate "Analog Devices AD5761/61R/21/21R DAC driver"
+	depends on SPI_MASTER
+	help
+	  Say yes here to build support for Analog Devices AD5761, AD5761R, AD5721,
+	  AD5721R Digital to Analog Converter.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad5761.
+
 config AD5764
 	tristate "Analog Devices AD5764/64R/44/44R DAC driver"
 	depends on SPI_MASTER