frontend/va: Keep track of some VP9 previous frame data for current frame use_prev_in_find_mvs_refs

Fixes: c8e8ce83 ("d3d12: Add VP9 Decode support")

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21694>
(cherry picked from commit 6fea823dc0a3accfc6e0cdae26ac88a08b806c61)
3 files changed