[bug fix]不使能LWIP的TCP功能时，编译出错。

components/net/lwip-2.0.2/src/api/api_lib.c

@@ -175,12 +175,12 @@ netconn_delete(struct netconn *conn)
 
   API_MSG_VAR_ALLOC(msg);
   API_MSG_VAR_REF(msg).conn = conn;
+#if LWIP_TCP
 #if LWIP_SO_SNDTIMEO || LWIP_SO_LINGER
   /* get the time we started, which is later compared to
      sys_now() + conn->send_timeout */
   API_MSG_VAR_REF(msg).msg.sd.time_started = sys_now();
 #else /* LWIP_SO_SNDTIMEO || LWIP_SO_LINGER */
-#if LWIP_TCP
   API_MSG_VAR_REF(msg).msg.sd.polls_left =
     ((LWIP_TCP_CLOSE_TIMEOUT_MS_DEFAULT + TCP_SLOW_INTERVAL - 1) / TCP_SLOW_INTERVAL) + 1;
 #endif /* LWIP_TCP */

components/net/lwip-2.1.0/src/api/api_lib.c

@@ -201,12 +201,12 @@ netconn_prepare_delete(struct netconn *conn)
 
   API_MSG_VAR_ALLOC(msg);
   API_MSG_VAR_REF(msg).conn = conn;
+#if LWIP_TCP
 #if LWIP_SO_SNDTIMEO || LWIP_SO_LINGER
   /* get the time we started, which is later compared to
      sys_now() + conn->send_timeout */
   API_MSG_VAR_REF(msg).msg.sd.time_started = sys_now();
 #else /* LWIP_SO_SNDTIMEO || LWIP_SO_LINGER */
-#if LWIP_TCP
   API_MSG_VAR_REF(msg).msg.sd.polls_left =
     ((LWIP_TCP_CLOSE_TIMEOUT_MS_DEFAULT + TCP_SLOW_INTERVAL - 1) / TCP_SLOW_INTERVAL) + 1;
 #endif /* LWIP_TCP */