avcodec/utils: correct align value for interplay

Fixes out of array access
Fixes: 452/fuzz-1-ffmpeg_VIDEO_AV_CODEC_ID_INTERPLAY_VIDEO_fuzzer

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
void ff_thread_await_progress(ThreadFrame *f, int progress, int field)
{
}

void ff_thread_await_progress(ThreadFrame *f, int progress, int field)
{
}
