iio: dac: ad5686: Add support for AD5674R/AD5679R

The AD5674R/AD5679R are low power, 16-channel, 12-/16-bit buffered voltage
output digital-to-analog converters (DACs). They include a 2.5 V internal
reference (enabled by default).

These devices are very similar to AD5684R/AD5686R, except that they have 16
channels.

Signed-off-by: Mircea Caprioru <mircea.caprioru@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
diff --git a/drivers/iio/dac/ad5686.h b/drivers/iio/dac/ad5686.h
index 19f6917..4c3e171 100644
--- a/drivers/iio/dac/ad5686.h
+++ b/drivers/iio/dac/ad5686.h
@@ -54,9 +54,11 @@ enum ad5686_supported_device_ids {
 	ID_AD5311R,
 	ID_AD5671R,
 	ID_AD5672R,
+	ID_AD5674R,
 	ID_AD5675R,
 	ID_AD5676,
 	ID_AD5676R,
+	ID_AD5679R,
 	ID_AD5681R,
 	ID_AD5682R,
 	ID_AD5683,