iio: dac: support the ad8460 Waveform DAC

iio: dac: support the ad8460 Waveform DAC

The AD8460 is a “bits in, power out” high voltage, high-power,
high-speed driver optimized for large output current (up to ±1 A)
and high slew rate (up to ±1800 V/μs) at high voltage (up to ±40 V)
into capacitive loads.

A digital engine implements user-configurable features: modes for
digital input, programmable supply current, and fault monitoring
and programmable protection settings for output current,
output voltage, and junction temperature. The AD8460 operates on
high voltage dual supplies up to ±55 V and a single low voltage
supply of 5 V.

Signed-off-by: Mariel Tinaco <Mariel.Tinaco@analog.com>
Link: https://patch.msgid.link/20240912095435.18639-3-Mariel.Tinaco@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>