iwlwifi: fix possible recursive locking deadlock

commit f84b29ec0a1ab767679d3f2428877b65f94bc3ff
Author: Johannes Berg <johannes.berg@intel.com>
Date:   Tue May 18 02:29:13 2010 -0700

    iwlwifi: queue user-initiated scan when doing internal scan

introduced a potential deadlock because it calls
ieee80211_scan_completed() with the priv->mutex
held, but mac80211 may call back into iwlwifi
which would lead to recursive locking. Move this
out from under the mutex.

Cc: stable@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>