[CFT]: filtered frames support

[Adrian Chadd]

Hi all,

I've been working on filtered frames support as a precursor for
correct AP mode power save support.

The patch is here:
http://people.freebsd.org/~adrian/ath/20120910-filter-frame-12-works.diff

It only supports filtered frames for 802.11n aggregate sessions. It
doesn't yet support filtered frames on non-aggregate sessions as I
haven't yet implemented a software retry mechanism for non-ADDBA
session transmission.

I'd like to commit this to -HEAD soon so I can work on software
retransmission for non-ADDBA session traffic.

Thanks again for helping me develop 802.11n support for the Atheros
wifi devices!




Adrian