iio: add mcp4725 I2C DAC driver

v5:
* fix warnings (Jonathan Cameron)

v4:
* remove unused indio_dev pointer in mcp4725_data (Jonathan Cameron)
* use u16 instead of unsigned short in mcp4725_data (Jonathan Cameron)
* #include mcp4725.h from linux/iio/dac/

v3:
* move from staging to drivers/iio
* switch to chan_spec
* dev_get_drvdata() -> dev_to_iio_dev()
* annotate probe() and remove() with __devinit and __devexit

v2 (based on comments from Jonathan Cameron and Lars-Peter Clausen):
* did NOT switch to chan_spec yet
* rebase to staging-next tree, update iio header locations
* dropped dac.h #include, not needed
* strict_strtol() -> kstrtol()
* call iio_device_unregister() in remove()
* everything in one patch

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index a626f03..92fb3a0 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -118,4 +118,15 @@
 	  This driver can also be built as a module.  If so, the module
 	  will be called max517.
 
+config MCP4725
+	tristate "MCP4725 DAC driver"
+	depends on I2C
+	---help---
+	  Say Y here if you want to build a driver for the Microchip
+	  MCP 4725 12-bit digital-to-analog converter (DAC) with I2C
+	  interface.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called mcp4725.
+
 endmenu