iio: light: Add support for APDS9306 Light Sensor

iio: light: Add support for APDS9306 Light Sensor

Driver support for Avago (Broadcom) APDS9306 Ambient Light Sensor.
It has two channels - ALS and CLEAR. The ALS (Ambient Light Sensor)
channel approximates the response of the human-eye providing direct
read out where the output count is proportional to ambient light levels.
It is internally temperature compensated and rejects 50Hz and 60Hz flicker
caused by artificial light sources. Hardware interrupt configuration is
optional. It is a low power device with 20 bit resolution and has
configurable adaptive interrupt mode and interrupt persistence mode.
The device also features inbuilt hardware gain, multiple integration time
selection options and sampling frequency selection options.

This driver also uses the IIO GTS (Gain Time Scale) Helpers Namespace for
Scales, Gains and Integration time implementation.

Signed-off-by: Subhajit Ghosh <subhajit.ghosh@tweaklogic.com>
Link: https://lore.kernel.org/r/20240309105031.10313-6-subhajit.ghosh@tweaklogic.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>