stm32f7 example starts on real h/w, with plus-TCP driver

src/net.c

@@ -115,7 +115,7 @@ void mg_mgr_free(struct mg_mgr *mgr) {
   struct mg_connection *c;
   for (c = mgr->conns; c != NULL; c = c->next) c->is_closing = 1;
   mg_mgr_poll(mgr, 0);
-#if MG_ARCH == MG_ARCH_FREERTOS
+#if MG_ARCH == MG_ARCH_FREERTOS_TCP
   FreeRTOS_DeleteSocketSet(mgr->ss);
 #endif
   LOG(LL_INFO, ("All connections closed"));