l2tp: Split pppol2tp patch into separate l2tp and ppp parts

This patch splits the pppol2tp driver into separate L2TP and PPP parts
to prepare for L2TPv3 support. In L2TPv3, protocols other than PPP can
be carried, so this split creates a common L2TP core that will handle
the common L2TP bits which protocol support modules such as PPP will
use.

Note that the existing pppol2tp module is split into l2tp_core and
l2tp_ppp by this change.

There are no feature changes here. Internally, however, there are
significant changes, mostly to handle the separation of PPP-specific
data from the L2TP session and to provide hooks in the core for
modules like PPP to access.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/if_pppol2tp.h b/include/linux/if_pppol2tp.h
index c58baea..1a1fb6e 100644
--- a/include/linux/if_pppol2tp.h
+++ b/include/linux/if_pppol2tp.h
@@ -2,7 +2,7 @@
  * Linux PPP over L2TP (PPPoL2TP) Socket Implementation (RFC 2661)
  *
  * This file supplies definitions required by the PPP over L2TP driver
- * (pppol2tp.c).  All version information wrt this file is located in pppol2tp.c
+ * (l2tp_ppp.c).  All version information wrt this file is located in l2tp_ppp.c
  *
  * License:
  *		This program is free software; you can redistribute it and/or