Fixes: signed integer overflow: 2082471995 * 36 cannot be represented in type 'int'
Fixes: 16025/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DDS_fuzzer-5136663778426880

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegReviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>