Merge pull request #110 from qiyongzhong0/fix_bc26_netdev_add

fix bc26_netdev_add

class/bc26/at_device_bc26.c

@@ -631,6 +631,12 @@ static struct netdev *bc26_netdev_add(const char *netdev_name)
 #define HWADDR_LEN          8
     struct netdev *netdev = RT_NULL;
 
+    netdev = netdev_get_by_name(netdev_name);
+    if(netdev != RT_NULL)
+    {
+        return(netdev);
+    }
+
     netdev = (struct netdev *)rt_calloc(1, sizeof(struct netdev));
     if (netdev == RT_NULL)
     {