vah265dec: Fix end_picture() vmethod.
Since commit 88437a9c the signature of h265decoder's end_picture() changed to return GstFlowReturn, but vah265dec was not updated.
This commit fixes this regression.
Since commit 88437a9c the signature of h265decoder's end_picture() changed to return GstFlowReturn, but vah265dec was not updated.
This commit fixes this regression.