ppp: declare ppp devices as enumerated interfaces

Let user space be aware of the naming scheme used by ppp interfaces
(visible in /sys/class/net/<iface>/name_assign_type).

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 1cd7651..fc8ad00 100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2726,8 +2726,7 @@
 	int ret = -ENOMEM;
 	int i;
 
-	dev = alloc_netdev(sizeof(struct ppp), "", NET_NAME_UNKNOWN,
-			   ppp_setup);
+	dev = alloc_netdev(sizeof(struct ppp), "", NET_NAME_ENUM, ppp_setup);
 	if (!dev)
 		goto out1;