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.