Merge branch 'l2tp-remove-unused-code'

Guillaume Nault says:

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l2tp: remove unused code

Patch #1 removes the ref/deref mechanism that was originally used to
prevent ppp pseudowires from dropping their sockets. This mechanism
was error prone and isn't used anymore.

Patch #2 removes some module specific refcount debugging.
Patches #3 and #4 take care of some dead code.
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Signed-off-by: David S. Miller <davem@davemloft.net>