iio: add MCP4728 I2C DAC driver
MCP4728 is a 12-bit quad channel DAC with I2C interface.
support for:
* per-channel gain
* per-channel power state
* per-channel power down mode control
* per-channel vref selection internal/vdd
* store current state to on-chip EEPROM
Signed-off-by: Andrea Collamati <andrea.collamati@gmail.com>
Link: https://lore.kernel.org/r/a0933003ed3c855f9d80d6ce0a40add2b6f0ba36.1691066050.git.andrea.collamati@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>