The "func_id"-based matching is very fuzzy and can lead to false positives.
Therefore, it should be tried to avoid relying on these matches. Until
most/all existing func_id-based matches are replaced by
manf_id/card_id/prod_id matches (a patch which will ask to send the
appropriate card information to the PCMCIA mailing list will be added once
other, more pressing issues are adressed), we need to emulate cardmgr
behaviour by allowing func_id matches if no manf_id/card_id/prod_id match
occurs. This can only be done in userspace because of modules possibly loaded
with long delays. So, add a per-device sysfs file for this purpose.