avcodec/cdxl: Fix signed integer overflow: 14243456 * 164 cannot be represented in type 'int'

Fixes: 1341/clusterfuzz-testcase-minimized-5441502618583040

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