iio: trigger: make stub functions static inline

Make sure that the trigger function stubs are all static inline.
Otherwise we might see compiler warnings about declared but unused
functions.

Fixes 77712e5f: ("Staging: iio: Staticise non-exported functions")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/iio_core_trigger.h

@@ -30,7 +30,7 @@ int iio_trigger_detach_poll_func(struct iio_trigger *trig,
  * iio_device_register_trigger_consumer() - set up an iio_dev to use triggers
  * @indio_dev: iio_dev associated with the device that will consume the trigger
  **/
-static int iio_device_register_trigger_consumer(struct iio_dev *indio_dev)
+static inline int iio_device_register_trigger_consumer(struct iio_dev *indio_dev)
 {
 	return 0;
 }
@@ -39,7 +39,7 @@ static int iio_device_register_trigger_consumer(struct iio_dev *indio_dev)
  * iio_device_unregister_trigger_consumer() - reverse the registration process
  * @indio_dev: iio_dev associated with the device that consumed the trigger
  **/
-static void iio_device_unregister_trigger_consumer(struct iio_dev *indio_dev)
+static inline void iio_device_unregister_trigger_consumer(struct iio_dev *indio_dev)
 {
 }