staging:iio:ad7291: add missing .driver_module to struct iio_info

Add missing .driver_module of struct iio_info. This prevents the
module from being removed from underneath its users.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/staging/iio/adc/ad7291.c

@@ -517,6 +517,7 @@ static const struct iio_info ad7291_info = {
 	.read_event_value = &ad7291_read_event_value,
 	.write_event_value = &ad7291_write_event_value,
 	.event_attrs = &ad7291_event_attribute_group,
+	.driver_module = THIS_MODULE,
 };
 
 static int ad7291_probe(struct i2c_client *client,