ath9k_htc: add AVM FRITZ!WLAN 11N v2 support

ath9k_htc: add AVM FRITZ!WLAN 11N v2 support

commit 8c34559b4a6df32e4af1b073397fa4dc189a5485 upstream.

This was reported and tested by Martin Walter over at AVM GmbH Berlin.
This also applies to 3.0.1 so sendint to stable.

Cc: s.kirste@avm.de
Cc: d.friedel@avm.de
Cc: Martin Walter <m.walter@avm.de>
Cc: Peter Grabienski <pgrabien@qca.qualcomm.com>
Tested-by: Martin Walter <m.walter@avm.de>
Signed-off-by: Luis R. Rodriguez <mcgrof@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>