avcodec/dirac_vlc: Fix invalid shift

Fixes: runtime error: shift exponent 65 is too large for 64-bit type 'residual' (aka 'unsigned long')
Fixes: 2737/clusterfuzz-testcase-minimized-4968639147016192

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