iio:gyro:itg3200 - drop unreachable return ret. Highlighted by smatch

CHECK   drivers/iio/gyro/itg3200_core.c
drivers/iio/gyro/itg3200_core.c:114 itg3200_read_raw() info: ignoring unreachable code.
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Cc: Neil Brown <neilb@suse.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>

drivers/iio/gyro/itg3200_core.c

@@ -110,8 +110,6 @@ static int itg3200_read_raw(struct iio_dev *indio_dev,
 	default:
 		return -EINVAL;
 	}
-
-	return ret;
 }
 
 static ssize_t itg3200_read_frequency(struct device *dev,