dt-bindings: iio: light: add support for Dyna-Image AL3010

The Dyna-Image AL3010 is a 16-bit digital ambient light sensor which
provides a multiple gain function with linear response over a dynamic
range 1216/4863/19452/77806.

Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>