Fixes: left shift of 233 by 24 places cannot be represented in type 'int'
Fixes: 20736/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_PCM_LXF_fuzzer-4829212685107200

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