[component][sal]delete netdev_lo

netdev_lo无需单独处理，可以根据协议去找对应的网络设备

components/net/netdev/include/netdev.h

@@ -111,8 +111,6 @@ struct netdev
 extern struct netdev *netdev_list;
 /* The default network interface device */
 extern struct netdev *netdev_default;
-/* The local virtual network device */
-extern struct netdev *netdev_lo;
 /* The network interface device ping response object */
 struct netdev_ping_resp
 {

components/net/netdev/src/netdev.c

@@ -35,8 +35,6 @@
 struct netdev *netdev_list = RT_NULL;
 /* The default network interface device */
 struct netdev *netdev_default = RT_NULL;
-/* The local virtual network device */
-struct netdev *netdev_lo = RT_NULL;
 /* The global network register callback */
 static netdev_callback_fn g_netdev_register_callback = RT_NULL;
 static netdev_callback_fn g_netdev_default_change_callback = RT_NULL;

components/net/sal/src/sal_socket.c

@@ -444,11 +444,6 @@ static int socket_init(int family, int type, int protocol, struct sal_socket **r
     struct netdev *netdev = RT_NULL;
     rt_bool_t flag = RT_FALSE;
 
-    if (family == AF_UNIX)
-    {
-        netdv_def = netdev_lo;
-    }
-
     if (family < 0 || family > AF_MAX)
     {
         return -1;