iio: light: vl6180: Correct ALS scale for non-default gain/integration time

The reported scale was only correct for the default settings of 100 ms
integration time and gain 1.

This aligns the reported scale with the behaviour of any other IIO driver
and the documented ABI, but may require userspace changes if someone uses
non-default settings.
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/vl6180.c

@@ -315,9 +315,12 @@ static int vl6180_read_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_SCALE:
 		switch (chan->type) {
 		case IIO_LIGHT:
-			*val = 0; /* one ALS count is 0.32 Lux */
-			*val2 = 320000;
-			break;
+			/* one ALS count is 0.32 Lux @ gain 1, IT 100 ms */
+			*val = 32000; /* 0.32 * 1000 * 100 */
+			*val2 = data->als_gain_milli * data->als_it_ms;
+
+			return IIO_VAL_FRACTIONAL;
+
 		case IIO_DISTANCE:
 			*val = 0; /* sensor reports mm, scale to meter */
 			*val2 = 1000;