Fixes: Timeout (250sec -> 6sec)
Fixes: 17627/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MSZH_fuzzer-5643017129558016

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>