avcodec/svq3: Fix multiple runtime error: signed integer overflow: 44161 * 61694 cannot be represented in type 'int'

Fixes: 1382/clusterfuzz-testcase-minimized-6013445293998080

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