if_rsu 11n - please test

[Adrian Chadd]

Hi!

I've added enough dsupport to if_rsu to do basic 11n. RX
aggregation/reordering works. It's enough to actually do 11n but it
still fails an iperf test.

To test:

* update to today's HEAD
* kldunload if_rsu; just to be sure
* kenv hw.usb.rsu.enable_11n=1
* insert if_rsu NIC
* check dmesg for "enabling 11n" or something like that.

Ifconfig wlanX should show 11g/ht20 or 11g/ht40 when it's associated.

See how it works for you. There are still transmit buffer exhaustion /
TX hangs that aren't recovered from and I'm still not convinced it's
transmitting at even remotely full TX power. That's next on my list.

Thanks!



-adrian