net: pppol2tp - introduce net-namespace functionality

- Each tunnel and appropriate lock are inside own namespace now.
- pppox code allows to create per-namespace sockets for
  both PX_PROTO_OE and PX_PROTO_OL2TP protocols. Actually since
  now pppox_create support net-namespaces new PPPo... protocols
  (if they ever will be) should support net-namespace too otherwise
  explicit check for &init_net would be needed.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/pppox.c

@@ -111,10 +111,6 @@ static int pppox_create(struct net *net, struct socket *sock, int protocol)
 	if (protocol < 0 || protocol > PX_MAX_PROTO)
 		goto out;
 
-	/* we support net-namespaces for PPPoE only (yet) */
-	if (protocol != PX_PROTO_OE && net != &init_net)
-		return -EAFNOSUPPORT;
-
 	rc = -EPROTONOSUPPORT;
 	if (!pppox_protos[protocol])
 		request_module("pppox-proto-%d", protocol);