avcodec/dsicinvideo: Fail if there is only a small fraction of the data available that comprises a full frame

Fixes: Timeout
Fixes: 6306/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DSICINVIDEO_fuzzer-5079253549842432

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