ifmedia_init() invocation. IFM_IMASK makes only sense here when all of
the maxium of 32 PHYs on each one MII bus support disjoint sets of media,
which generally isn't the case (though it would be nice if we had a way
to let NIC drivers indicate that for the few card models where the PHY
configuration is known/fixed and IFM_IMASK actually makes sense).
- Add and use a miibus_print_child() for the bus_print_child method which
additionally prints the PHY number (which actually is the PHY address)
so one can figure out the media instance <-> PHY number mapping from the
PHY driver attach output. This is intented to be usefull in situations
where the addresses of the PHYs on the bus are known (f.e. of internal/
integrated PHYs) so one can feed the appropriate media instance number
to ifconfig(8) (with the upcoming change for ifconfig(8)).
This is more or less inspired by the NetBSD mii_print().