dummy: declare dummy devices as enumerated devices

Dummy device name is enumerated by the kernel, let user space be aware
of the naming scheme used by dummy devices:
(visible in /sys/class/net/<iface>/name_assign_type).

Signed-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/dummy.c b/drivers/net/dummy.c
index d0a1f9c..e31ab3b 100644
--- a/drivers/net/dummy.c
+++ b/drivers/net/dummy.c
@@ -388,7 +388,7 @@
 	int err;
 
 	dev_dummy = alloc_netdev(sizeof(struct dummy_priv),
-				 "dummy%d", NET_NAME_UNKNOWN, dummy_setup);
+				 "dummy%d", NET_NAME_ENUM, dummy_setup);
 	if (!dev_dummy)
 		return -ENOMEM;