iio:dac:ad5686: Add AD5311R support

AD5311R is a single channel DAC with 10-bit precision and i2c interface.
The device includes a 2.5V internal reference which is enabled by default.

This device is similar to AD5691R/AD5692R/AD5693/AD5693R, the only
difference is that it has 10-bit precision.

Datasheet:
http://www.analog.com/media/en/technical-documentation/data-sheets/AD5310R_5311R.pdf

Signed-off-by: Stefan Popa <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/dac/ad5686.c

···
 		AD5868_CHANNEL(7, 7, bits, _shift),		\
 }
 
+DECLARE_AD5693_CHANNELS(ad5311r_channels, 10, 6);
 DECLARE_AD5676_CHANNELS(ad5672_channels, 12, 4);
 DECLARE_AD5676_CHANNELS(ad5676_channels, 16, 0);
 DECLARE_AD5686_CHANNELS(ad5684_channels, 12, 4);
···
 DECLARE_AD5693_CHANNELS(ad5691r_channels, 12, 4);
 
 static const struct ad5686_chip_info ad5686_chip_info_tbl[] = {
+	[ID_AD5311R] = {
+		.channels = ad5311r_channels,
+		.int_vref_mv = 2500,
+		.num_channels = 1,
+		.regmap_type = AD5693_REGMAP,
+	},
 	[ID_AD5671R] = {
 		.channels = ad5672_channels,
 		.int_vref_mv = 2500,

drivers/iio/dac/ad5686.h

···
  * ad5686_supported_device_ids:
  */
 enum ad5686_supported_device_ids {
+	ID_AD5311R,
 	ID_AD5671R,
 	ID_AD5672R,
 	ID_AD5675R,

drivers/iio/dac/ad5696-i2c.c

···
 }
 
 static const struct i2c_device_id ad5686_i2c_id[] = {
+	{"ad5311r", ID_AD5311R},
 	{"ad5671r", ID_AD5671R},
 	{"ad5675r", ID_AD5675R},
 	{"ad5691r", ID_AD5691R},