iio: core: remove iio_priv_to_dev() helper

All users of this helper have been updated to not use it.
Remove it now, so that we don't need to move it when creating the
iio_dev_opaque structure.
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

include/linux/iio/iio.h

@@ -689,12 +689,6 @@ static inline void *iio_priv(const struct iio_dev *indio_dev)
 	return indio_dev->priv;
 }
 
-static inline struct iio_dev *iio_priv_to_dev(void *priv)
-{
-	return (struct iio_dev *)((char *)priv -
-				  ALIGN(sizeof(struct iio_dev), IIO_ALIGN));
-}
-
 void iio_device_free(struct iio_dev *indio_dev);
 struct iio_dev *devm_iio_device_alloc(struct device *parent, int sizeof_priv);
 struct iio_trigger *devm_iio_trigger_alloc(struct device *dev,