use TAILQ macros. The sk_attach_xmac() routine calls sk_init_xmac()
before doing the transceiver probe, but *before* ether_ifattach()
is called. This causes sk_init_xmac() to call sk_setmulti(), which
tries to do a TAILQ_FOREACH(), which it can't do because ether_ifattach()
hasn't done a TAILQ_INIT() yet. This causes a NULL pointer dereference
and panic in sk_setmulti() at driver load/initialization time.
Fixed by calling ether_ifattach() before the MII probe.
The code in RELENG_4 still uses the old way of enumerating the
multicast list and doesn't have this problem. Yet.
68e691b2ab