iio: dac: New driver for AD5686R, AD5685R, AD5684R Digital to analog converters

New driver for AD5686R, AD5685R, AD5684R Quad channel digital to analog converters

Changes since V1:

drop header file
use strtobool()
Fix dev attribute macros
Reorder probe() function

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/staging/iio/dac/Makefile b/drivers/staging/iio/dac/Makefile
index 83196de..7f4f2ed 100644
--- a/drivers/staging/iio/dac/Makefile
+++ b/drivers/staging/iio/dac/Makefile
@@ -6,4 +6,5 @@
 obj-$(CONFIG_AD5504) += ad5504.o
 obj-$(CONFIG_AD5446) += ad5446.o
 obj-$(CONFIG_AD5791) += ad5791.o
+obj-$(CONFIG_AD5686) += ad5686.o
 obj-$(CONFIG_MAX517) += max517.o