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: NGuillaume Nault <g.nault@alphalink.fr>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ppp/ppp_generic.c

@@ -2726,8 +2726,7 @@ static struct ppp *ppp_create_interface(struct net *net, int unit,
 	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;