Hints-only devices should have BUS_PROBE_NOWILDCARD set. We probably need
a better flag for this (in the driver metadata, for example).
OS X 10.9 added.
These nexus attachments do not execute a real probe and so need
BUS_PROBE_NOWILDCARD set.
Hints-only devices should return BUS_PROBE_NOWILDCARD from their probe
methods.