contrib: ffmpeg: fix DXVA MPEG2 output
The updated patch doesn't meet the underlying libavcodec changes. The VC-1 patch is not needed as the merged version upstream is sufficient.
The MPEG-2 patch is done in a similar way as the VC-1 patch.
The check was added for VC-1 in https://github.com/FFmpeg/FFmpeg/commit/fe6037fd04db8837dcdb9013f9c4ad4e7eb0592e but not MPEG-2.
Fixes #28855
Edited by Steve Lhomme