[lwIP] Fix the usage issue of NETIF_LINK_CALLBACK.

components/net/lwip-1.4.1/src/arch/sys_arch.c

@@ -108,7 +108,7 @@ static void tcpip_init_done_callback(void *arg)
                 netif_set_up(ethif->netif);
             }
 
-#ifdef LWIP_NETIF_LINK_CALLBACK
+#if LWIP_NETIF_LINK_CALLBACK
             netif_set_link_up(ethif->netif);
 #endif