avcodec/hq_hqa: Fix: runtime error: signed integer overflow: -255 * 10180917 cannot be represented in type 'int'

Fixes: 1626/clusterfuzz-testcase-minimized-6416580571299840

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