MFC r220873, r220897, r220905.

MFC r220873, r220897, r220905.

r220873:
- Move all Ethernet specific items from sge_eq to sge_txq.  sge_eq is
  now a suitable base for all kinds of egress queues.

- Add control queues (sge_ctrlq) and allocate one of these per hardware           channel.  They can be used to program filters and steer traffic (and
  more).

r220897:
Use the correct free routine when destroying a control queue.

r220905:
Ring the freelist doorbell from within refill_fl.  While here, fix a bug
that could have allowed the hardware pidx to reach the cidx even though
the freelist isn't empty.  (Haven't actually seen this but it was there
waiting to happen..)

git-svn-id: svn://svn.freebsd.org/base/stable/8@221120 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f