cfg80211: ignore spurious deauth

Ever since mac80211/drivers are no longer
fully in charge of keeping track of the
auth status, trying to make them do so will
fail. Instead of warning and reporting the
deauthentication to userspace, cfg80211 must
simply ignore it so that spurious
deauthentications, e.g. before starting
authentication, aren't seen by userspace as
actual deauthentications.

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