avcodec/asvdec: Use rounded up dimenensions in input size check

Fixes: Timeout
Fixes: 2001/clusterfuzz-testcase-minimized-6187599389523968

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