staging:iio:ad7780: Report scale as fractional value

Move the complexity of calculating the fixed point scale to the core.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/ad7780.c

@@ -90,17 +90,14 @@ static int ad7780_read_raw(struct iio_dev *indio_dev,
 			   long m)
 {
 	struct ad7780_state *st = iio_priv(indio_dev);
-	unsigned long scale_uv;
 
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
 		return ad_sigma_delta_single_conversion(indio_dev, chan, val);
 	case IIO_CHAN_INFO_SCALE:
-		scale_uv = (st->int_vref_mv * 100000 * st->gain)
-			>> (chan->scan_type.realbits - 1);
-		*val =  scale_uv / 100000;
-		*val2 = (scale_uv % 100000) * 10;
-		return IIO_VAL_INT_PLUS_MICRO;
+		*val = st->int_vref_mv * st->gain;
+		*val2 = chan->scan_type.realbits - 1;
+		return IIO_VAL_FRACTIONAL_LOG2;
 	case IIO_CHAN_INFO_OFFSET:
 		*val -= (1 << (chan->scan_type.realbits - 1));
 		return IIO_VAL_INT;