Reject attempts to attack a disk device that has the old NEEDSGIANT
flag set.

Reviewed by:	mav
Add id for GTM661W.
Temporarily disable multi-rate retry (link quality) and eliminate rate
index lookups.

* My recent(ish) change to iwn(4) and the net80211 rate control API to
  support 11n rates broke the link quality table use.  So, until I or
  someone else decides to fix it, let's just disable it for now.

* Teach iwn_tx_data_raw() to use the iwn_rate_to_plcp() function.

* Eliminate two uses of the net80211 rate index lookup functions - they
  are only for legacy rates and they're not needed here.

This fixes some invalid looking rate control TX issues that showed up
on my 4965 but it doesn't fix the two TX hangs I've noticed. Those look
like DMA related issues.

Tested:

* 4965, STA mode
* 5100, STA mode
Begin fleshing out a knob to enable/disable bluetooth coexistence.

Some firmware versions seem to get very unhappy if they're sent btcoex
commands when they don't actually have bluetooth hardware in them.
So, disable sending them those commands.

Tested:

* 5100 (which has bluetooth, no problems)
* 4965 (which doesn't have bluetooth, but didn't seem to crash)
* 6200 (no bluetooth, seems to get unhappy being sent bluetooth commands.)
vnet.h needs to be included before raw_cb.h. Now it compiles due to
pollution via if_var.h.