BugID:21213413:Enable network loopback  interface on rda5981
/**
* Loopback demo related options.
*/
-//#define LWIP_NETIF_LOOPBACK 1
-//#define LWIP_HAVE_LOOPIF 1
-//#define LWIP_NETIF_LOOPBACK_MULTITHREADING 1
-//#define LWIP_LOOPBACK_MAX_PBUFS 8
+#define LWIP_NETIF_LOOPBACK 1
+#define LWIP_HAVE_LOOPIF 1
+#define LWIP_NETIF_LOOPBACK_MULTITHREADING 1
+#define LWIP_LOOPBACK_MAX_PBUFS 8
#define TCPIP_THREAD_NAME "tcp/ip"
#define TCPIP_THREAD_STACKSIZE 3072
