iio: dac: ad5446: Add IDs of compatible Texas Instruments chips

The Texas Instruments DAC081S101, DAC101S101 and DAC121S101 have the
exact same pinout, programming interface and power-down modes as the
AD5300, AD5310 and AD5320, respectively, and their datasheets declare
them "a direct replacement" for the Analog Devices chips.  This may
not be immediately obvious to a casual observer, so add them to the
supported modalias strings.

Datasheets:
http://www.ti.com/lit/ds/symlink/dac081s101.pdf
http://www.ti.com/lit/ds/symlink/dac101s101.pdf
http://www.ti.com/lit/ds/symlink/dac121s101.pdf
http://www.analog.com/media/en/technical-documentation/data-sheets/AD5300.pdf
http://www.analog.com/media/en/technical-documentation/data-sheets/AD5310.pdf
http://www.analog.com/media/en/technical-documentation/data-sheets/AD5320.pdf



Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>