ffmpeg: fix for CVE-2022-48434

ffmpeg: fix for CVE-2022-48434

libavcodec/pthread_frame.c in FFmpeg before 5.1.2, as used in VLC and
other products, leaves stale hwaccel state in worker threads, which
allows attackers to trigger a use-after-free and execute arbitrary
code in some circumstances (e.g., hardware re-initialization upon a
mid-video SPS change when Direct3D11 is used).

Signed-off-by: Narpat Mali <narpat.mali@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>