cfg80211: free sme on connection failures

cfg80211 is notified about connection failures by
__cfg80211_connect_result() call. However, this
function currently does not free cfg80211 sme.

This results in hanging connection attempts in some cases

e.g. when mac80211 authentication attempt is denied,
we have this function call:
ieee80211_rx_mgmt_auth() -> cfg80211_rx_mlme_mgmt() ->
cfg80211_process_auth() -> cfg80211_sme_rx_auth() ->
__cfg80211_connect_result()

but cfg80211_sme_free() is never get called.

Fixes: ceca7b71 ("cfg80211: separate internal SME implementation")
Cc: stable@vger.kernel.org (3.10+)
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>