really make starpu_bcsr_filter_canonical_block_child_ops return what it should

include/starpu_data_filters.h

@@ -322,7 +322,7 @@ void starpu_bcsr_filter_canonical_block(void *father_interface, void *child_inte
 /**
    Return the child_ops of the partition obtained with starpu_bcsr_filter_canonical_block().
 */
-void starpu_bcsr_filter_canonical_block_child_ops(struct starpu_data_filter *f, unsigned child);
+struct starpu_data_interface_ops *starpu_bcsr_filter_canonical_block_child_ops(struct starpu_data_filter *f, unsigned child);
 
 /** @} */
 

src/datawizard/interfaces/bcsr_filters.c

@@ -51,7 +51,7 @@ void starpu_bcsr_filter_canonical_block(void *father_interface, void *child_inte
 	}
 }
 
-void starpu_bcsr_filter_canonical_block_child_ops(STARPU_ATTRIBUTE_UNUSED struct starpu_data_filter *f, unsigned child)
+struct starpu_data_interface_ops *starpu_bcsr_filter_canonical_block_child_ops(STARPU_ATTRIBUTE_UNUSED struct starpu_data_filter *f, unsigned child)
 {
 	return &starpu_interface_matrix_ops;
 }