iio: ad_sigma_delta: Remove no-op trigger ops

The IIO core handles a trigger ops with all NULL callbacks the
same as if the trigger ops itself was NULL.

Remove the empty trigger ops from the interrupt trigger driver to slightly
reduce the boilerplate code. Object size of the driver module is also
slightly reduced.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20211031142130.20791-3-lars@metafoo.deSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/adc/ad_sigma_delta.c

@@ -467,9 +467,6 @@ int ad_sd_validate_trigger(struct iio_dev *indio_dev, struct iio_trigger *trig)
 }
 EXPORT_SYMBOL_GPL(ad_sd_validate_trigger);
 
-static const struct iio_trigger_ops ad_sd_trigger_ops = {
-};
-
 static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_dev)
 {
 	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
@@ -486,7 +483,6 @@ static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_de
 	if (sigma_delta->trig == NULL)
 		return -ENOMEM;
 
-	sigma_delta->trig->ops = &ad_sd_trigger_ops;
 	init_completion(&sigma_delta->completion);
 
 	sigma_delta->irq_dis = true;