LOR in if_detach

[Jeffrey Hsu]

  > I must stop the interface before calling if_detach.

The midway driver doesn't do that now anyways, so there's no reason to
start now.

  > If I unlock after stoping before detaching, I get a race window
  > where somebody could just UP the interface.

This race is outside the scope of the network driver lock.

  > While thinking about, it seems, that having a lock in struct ifnet would
  > make sense in the long run. How can we otherwise ensure, that nobody is
  > calling if_ioctl while we are detaching the interface?

That's what I had planned.

							Jeffrey