iio: light: Add support for TI OPT4001 light sensor

iio: light: Add support for TI OPT4001 light sensor

This driver uses the continuous mode of the chip and integration
time can be configured through sysfs.
The constants for calculating lux value differs between packaging
so it uses different compatible string for the two versions
"ti,opt4001-picostar" and "ti,opt4001-sot-5x3" since the device id
is the same.

Datasheet: https://www.ti.com/lit/gpn/opt4001
Signed-off-by: Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@axis.com>
Link: https://lore.kernel.org/r/20230323-add-opt4001-driver-v3-2-62e121dab294@axis.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>