fix 11a channel use; mark OFDM operation correctly

Submitted by: Lucius Windschuh <lwindschuh@googlemail.com>

Merge from HEAD

Create a taskqueue for each wireless interface which provides a serialised
sleepable context for net80211 driver callbacks. This removes the need for USB
and firmware based drivers to roll their own

Create a taskqueue for each wireless interface which provides a serialised
sleepable context for net80211 driver callbacks. This removes the need for USB
and firmware based drivers to roll their own code to defer the chip programming
for state changes, scan requests, channel changes and mcast/promisc updates.
When a driver callback completes the hardware state is now guaranteed to have
been updated and is in sync with net80211 layer.

This nukes around 1300 lines of code from the wireless device drivers making
them more readable and less race prone.

The net80211 layer has been updated as follows
- all state/channel changes are serialised on the taskqueue.
- ieee80211_new_state() always queues and can now be called from any context
- scanning runs from a single taskq function and executes to completion. driver
callbacks are synchronous so the channel, phy mode and rx filters are
guaranteed to be set in hardware before probe request frames are
transmitted.

Help and contributions from Sam Leffler.

Reviewed by: sam

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- Merge from HEAD

Catch up with usb2_config struct layout changes.

Add uath(4) wireless USB driver for Atheros AR5005UG and AR5005UX
chipsets.

Reviewed by: sam