iio: light: acpi-als: Report data as processed

iio: light: acpi-als: Report data as processed

As per the ACPI specification (Revision 5.0) [1], the data coming
from the sensor represent the ambient light illuminance reading
expressed in lux. So use IIO_CHAN_INFO_PROCESSED to signify that
the data are pre-processed.

However, to keep backward ABI compatibility, the IIO_CHAN_INFO_RAW
bit is not removed.

[1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf

This issue has also been responsible for at least one userspace bug
report hence marking what is a small semantic fix really for stable.
[2] https://github.com/hadess/iio-sensor-proxy/issues/46

Signed-off-by: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>