staging:iio:adis16260: Use sign_extend32() instead of open-coding it

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/gyro/adis16260_core.c

@@ -277,9 +277,7 @@ static int adis16260_read_raw(struct iio_dev *indio_dev,
 			mutex_unlock(&indio_dev->mlock);
 			return ret;
 		}
-		val16 &= (1 << bits) - 1;
-		val16 = (s16)(val16 << (16 - bits)) >> (16 - bits);
-		*val = val16;
+		*val = sign_extend32(val16, bits - 1);
 		mutex_unlock(&indio_dev->mlock);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_CALIBSCALE: