iio: dac: ti-dac5571: Add DAC081C081 support

The DAC081C081 is a TI DAC whose software interface is compatible with
the DAC5571. It is the 8-bit version of the DAC121C081, already
supported by the DAC5571 driver. Extends the driver to support this
chip.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Sean Nyekjaer &lt;sean@geanix.com <mailto:sean@geanix.com&gt;>
Link: https://lore.kernel.org/r/20240325203245.31660-3-laurent.pinchart@ideasonboard.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>