staging: iio: cdc: fix improper return value

At the end of function ad7150_write_event_config(), directly returns 0.
As a result, the errors will be ignored by the callers. It may be better
to return variable "ret".
Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/cdc/ad7150.c

@@ -274,7 +274,7 @@ static int ad7150_write_event_config(struct iio_dev *indio_dev,
 error_ret:
 	mutex_unlock(&chip->state_lock);
 
-	return 0;
+	return ret;
 }
 
 static int ad7150_read_event_value(struct iio_dev *indio_dev,