avcodec/wmv2dsp: Fix runtime error: signed integer overflow: 181 * -17047030 cannot be represented in type 'int'

Fixes: 1503/clusterfuzz-testcase-minimized-5369271855087616

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