iwlwifi: force scan complete after timeout

If we do not get notification from hardware about scan complete, after
timeout do mac80211 scan completion anyway. This assure we end scan
in case of firmware hung.

Patch fix one of the causes of wdev_cleanup_work warning reported at
https://bugzilla.redhat.com/show_bug.cgi?id=593566

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Wey-Yi W Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>