dt-bindings: iio: light: Document TI OPT4001 light sensor

Add devicetree bindings for opt4001 ambient light sensor.

Signed-off-by: Stefan Windfeldt-Prytz <stefan.windfeldt-prytz@axis.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20230323-add-opt4001-driver-v3-1-62e121dab294@axis.com


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