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>

drivers/iio/light/acpi-als.c

@@ -54,7 +54,9 @@ static const struct iio_chan_spec acpi_als_channels[] = {
 			.realbits	= 32,
 			.storagebits	= 32,
 		},
-		.info_mask_separate	= BIT(IIO_CHAN_INFO_RAW),
+		/* _RAW is here for backward ABI compatibility */
+		.info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |
+					  BIT(IIO_CHAN_INFO_PROCESSED),
 	},
 };
 
@@ -152,7 +154,7 @@ static int acpi_als_read_raw(struct iio_dev *indio_dev,
 	s32 temp_val;
 	int ret;
 
-	if (mask != IIO_CHAN_INFO_RAW)
+	if ((mask != IIO_CHAN_INFO_PROCESSED) && (mask != IIO_CHAN_INFO_RAW))
 		return -EINVAL;
 
 	/* we support only illumination (_ALI) so far. */