sstate-cache-management: improve shown numbers of removed files

* deleted files were counting .siginfo and .done files, but total_files were counting only .tgz archives
  so it could show confusing output like:
  Figuring out the sstate:xxx_packagedata.tgz ... (21098 from 15162 files for packagedata suffix will be removed)
* split the counts and show both
* fix .sigdata sometimes used instead of .siginfo

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>