This patch adds sanity-checks for the beacon timers and especially the ATIM
window to ath5k. It is basically the same what i did for madwifi two years ago
and fixes a problem in IBSS mode which has been described as "ramping" pings.

See the code comments for a more detailed description and these links:

http://madwifi-project.org/ticket/1154
http://madwifi-project.org/changeset/3867
http://thread.gmane.org/gmane.linux.drivers.madwifi.devel/6066Signed-off-by: NBruno Randolf <br1@einfach.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>