video: adf: add supported formats to adf_overlay_engine_data

Change-Id: If2aa783b9ece60160f465bf697508fc58682e1bc
Signed-off-by: Greg Hackmann <ghackmann@google.com>
diff --git a/include/video/adf.h b/include/video/adf.h
index 6c2191a..eb7b9be 100644
--- a/include/video/adf.h
+++ b/include/video/adf.h
@@ -374,7 +374,8 @@
  * @base: common operations (see &struct adf_obj_ops)
  *
  * @supported_formats: list of fourccs the overlay engine can scan out
- * @n_supported_formats: length of supported_formats
+ * @n_supported_formats: length of supported_formats, up to
+ *	ADF_MAX_SUPPORTED_FORMATS
  */
 struct adf_overlay_engine_ops {
 	const struct adf_obj_ops base;