tools/target_dec_fuzzer: Adjust threshold for MMVIDEO

Fixes: Timeout
Fixes: 49003/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MMVIDEO_fuzzer-5550368423018496

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg


Reviewed-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

tools/target_dec_fuzzer.c

@@ -246,6 +246,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     case AV_CODEC_ID_LOCO:        maxpixels  /= 1024;  break;
     case AV_CODEC_ID_VORBIS:      maxsamples /= 1024;  break;
     case AV_CODEC_ID_LSCR:        maxpixels  /= 16;    break;
+    case AV_CODEC_ID_MMVIDEO:     maxpixels  /= 256;   break;
     case AV_CODEC_ID_MOTIONPIXELS:maxpixels  /= 256;   break;
     case AV_CODEC_ID_MP4ALS:      maxsamples /= 65536; break;
     case AV_CODEC_ID_MSA1:        maxpixels  /= 16384; break;