iio: adc: ti-ads7924: add Texas Instruments ADS7924 driver

The Texas Instruments ADS7924 is a 4 channels, 12-bit analog to
digital converter (ADC) with an I2C interface.

Datasheet: https://www.ti.com/lit/gpn/ads7924


Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20230115170623.3680647-2-hugo@hugovil.com


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