Plane: fixed FS_GCS_ENABL=2 for hearbeat failsafe

ArduPlane/system.cpp

@@ -351,7 +351,8 @@ void Plane::check_long_failsafe()
                    failsafe.last_heartbeat_ms != 0 &&
                    (tnow - failsafe.last_heartbeat_ms) > g.fs_timeout_long*1000) {
             failsafe_long_on_event(FAILSAFE_GCS, ModeReason::GCS_FAILSAFE);
-        } else if (g.gcs_heartbeat_fs_enabled == GCS_FAILSAFE_HEARTBEAT &&
+        } else if ((g.gcs_heartbeat_fs_enabled == GCS_FAILSAFE_HEARTBEAT ||
+                    g.gcs_heartbeat_fs_enabled == GCS_FAILSAFE_HB_RSSI) &&
                    failsafe.last_heartbeat_ms != 0 &&
                    (tnow - failsafe.last_heartbeat_ms) > g.fs_timeout_long*1000) {
             failsafe_long_on_event(FAILSAFE_GCS, ModeReason::GCS_FAILSAFE);