Use the workqueue provided by the mac80211 stack instead of the system
default queue.

Modified to use new ieee_queue_work() as required by changes in the
stack.
Signed-off-by: Juuso Oikarinen <juuso.oikarinen@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>