iio: mag3110: Use scan_type when processing raw data

Use channel definition as root of trust and replace constant
when reading elements directly using the raw sysfs attributes.

Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Link: https://lore.kernel.org/r/20211104082413.3681212-11-gwendal@chromium.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/magnetometer/mag3110.c

@@ -291,7 +291,8 @@ static int mag3110_read_raw(struct iio_dev *indio_dev,
 			if (ret < 0)
 				goto release;
 			*val = sign_extend32(
-				be16_to_cpu(buffer[chan->scan_index]), 15);
+				be16_to_cpu(buffer[chan->scan_index]),
+					    chan->scan_type.realbits - 1);
 			ret = IIO_VAL_INT;
 			break;
 		case IIO_TEMP: /* in 1 C / LSB */
@@ -306,7 +307,8 @@ static int mag3110_read_raw(struct iio_dev *indio_dev,
 			mutex_unlock(&data->lock);
 			if (ret < 0)
 				goto release;
-			*val = sign_extend32(ret, 7);
+			*val = sign_extend32(ret,
+					     chan->scan_type.realbits - 1);
 			ret = IIO_VAL_INT;
 			break;
 		default: