afsd: correct printf format mismatch in debugging printf

On platforms where size_t is unsigned int, the type of
cacheFiles * sizeof(AFSD_INO_T) is not an unsigned long as the format
string requires.  Casting cacheFiles to unsigned long ensures that the
result is at least unsigned long, although it will still be wrong if
any architecture makes size_t be long long.  Fixes build for FreeBSD
10 on i386.

Change-Id: Ifd124d81b16f53133293dd591f7f8cf2f7d3175a
Reviewed-on: http://gerrit.openafs.org/11384
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>