patches for if_iwi and wlan for WEP mode

[Mitsuru IWASAKI]

> > In RELENG_7, data frame is transmitted by iwi_tx_start() like this.
> > 
> >   ether_output
> >     ether_output_frame
> >       IFQ_HANDOFF/IFQ_HANDOFF_ADJ
> >         if_start
> >           iwi_start
> >             iwi_tx_start
> > 
> > After 8.0-RELEASE, device specific if_transmit() is called via net80211 layer.
> > 
> >   ether_output
> >     ether_output_frame
> >       if_transmit
> >         IFQ_HANDOFF/IFQ_HANDOFF_ADJ
> >           if_start
> >             ieee80211_start
> >               parent->if_transmit(ie. iwi_transmit())
> > 
> > There was not if_transmit method in iwi(4), so I add it.
> > On if_qflush(), CURRENT kernel complains that `transmit and qflush
> > must both either be set or both be NULL' from if.c.
> > I wrote iwi_qflush(), but actually never tested it...
> 
> Hmm, it still is the case for >= 8 afaik, there is a default
> if_transmit() which is used for all wireless drivers which seems to
> work pretty well. That's why I'm wondering, iwi(4) would be the first
> driver to have it's own if_transmit() function. I'm not aware of any
> technical reason for adding one, or did I miss something? If not I'd
> rather not have one added, for sake of consistency.

By your this comment, I noticed that my understanding on iwi_start()
call stack > 8.0 was wrong a bit, correct one is like this;

  ether_output
    ether_output_frame
      if_transmit
        IFQ_HANDOFF/IFQ_HANDOFF_ADJ
          if_start
            ieee80211_start
              parent->if_transmit(ie. if_transmit())
                IFQ_HANDOFF/IFQ_HANDOFF_ADJ
                  if_start
                    iwi_start
                      iwi_start_locked
                        iwi_tx_start

So iwi_transmit and iwi_qflush would not be necessary.

Today's version of patches at:
http://people.freebsd.org/~iwasaki/iwi/iwi-20120307.diff

This would be the final version I hope.

Thanks!