multimedia/dav1d: update to 0.7.1

Changes: https://code.videolan.org/videolan/dav1d/tags/0.7.1
Changes: https://code.videolan.org/videolan/dav1d/blob/0.7.1/NEWS
Changes: https://code.videolan.org/videolan/dav1d/compare/0.7.0...0.7.1
Reported by: Repology