iwlwifi: mvm: don't WARN when statistics are handled late

Since the statistics handler is asynchrous, it can very well
be that we will handle the statistics (hence the RSSI
fluctuation) when we already disassociated.
Don't WARN on this case.

This solves: https://bugzilla.redhat.com/show_bug.cgi?id=1071998

Cc: <stable@vger.kernel.org> [3.10+]
Fixes: 2b76ef13086f ("iwlwifi: mvm: implement reduced Tx power")
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

drivers/net/wireless/iwlwifi/mvm/bt-coex.c

@@ -872,8 +872,11 @@ void iwl_mvm_bt_rssi_event(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
 
 	lockdep_assert_held(&mvm->mutex);
 
-	/* Rssi update while not associated ?! */
-	if (WARN_ON_ONCE(mvmvif->ap_sta_id == IWL_MVM_STATION_COUNT))
+	/*
+	 * Rssi update while not associated - can happen since the statistics
+	 * are handled asynchronously
+	 */
+	if (mvmvif->ap_sta_id == IWL_MVM_STATION_COUNT)
 		return;
 
 	/* No BT - reports should be disabled */