staging:iio:adc:ad799x trivial: use the convenient chan struct.

This is much cleaner than bouncing through the various structures
to get to the same thing.
Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/adc/ad799x_core.c

@@ -158,12 +158,11 @@ static int ad799x_read_raw(struct iio_dev *dev_info,
 
 		if (ret < 0)
 			return ret;
-		*val = (ret >> st->chip_info->channel[0].scan_type.shift) &
-			RES_MASK(st->chip_info->channel[0].scan_type.realbits);
+		*val = (ret >> chan->scan_type.shift) &
+			RES_MASK(chan->scan_type.realbits);
 		return IIO_VAL_INT;
 	case (1 << IIO_CHAN_INFO_SCALE_SHARED):
-		scale_uv = (st->int_vref_mv * 1000)
-			>> st->chip_info->channel[0].scan_type.realbits;
+		scale_uv = (st->int_vref_mv * 1000) >> chan->scan_type.realbits;
 		*val =  scale_uv / 1000;
 		*val2 = (scale_uv % 1000) * 1000;
 		return IIO_VAL_INT_PLUS_MICRO;