probe method return BUS_PROBE_NOWILDCARD so it doesn't get attached to real
devices hanging off of nexus(4) with no specific devclass set. Actually, the
more desirable fix for this would be to get rid of the newbus interface of
cryptosoft(4) altogether but apparently crypto(9) was written with support
for cryptographic hardware in mind so that approach would require some KPI
breaking changes which don't seem worth it.
MFC after: 1 week
86c585d929