iio:trigger: Add helper function to verify that a trigger belongs to the same device

Some triggers can only be attached to the IIO device that corresponds to
the same physical device. Currently each driver that requires this
implements its own trigger validation function.

Introduce a new helper function called iio_trigger_validate_own_device()
that can be used to do this check. Having a common implementation avoids
code duplication and unnecessary boiler-plate code.

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

include/linux/iio/trigger.h

@@ -170,6 +170,8 @@ void iio_trigger_free(struct iio_trigger *trig);
  */
 bool iio_trigger_using_own(struct iio_dev *indio_dev);
 
+int iio_trigger_validate_own_device(struct iio_trigger *trig,
+				     struct iio_dev *indio_dev);
 
 #else
 struct iio_trigger;