cfg80211/mac80211: avoid state mishmash on deauth

Avoid situation when we are on associate state in mac80211 and
on disassociate state in cfg80211. This can results on crash
during modules unload (like showed on this thread:
http://marc.info/?t=134373976300001&r=1&w=2) and possibly other
problems.

Reported-by: Pedro Francisco <pedrogfrancisco@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>