avcodec/svq3: Fix runtime error: signed integer overflow: 169 * 12717677 cannot be represented in type 'int'

Fixes: 1556/clusterfuzz-testcase-minimized-5027865978470400

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