net: remove unnecessary return's

One of my pet coding style peeves is the practice of
adding extra return; at the end of function.
Kill several instances of this in network code.

I suppose some coccinelle wizardy could do this automatically.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_core.c

@@ -1809,8 +1809,6 @@ void l2tp_session_free(struct l2tp_session *session)
 	}
 
 	kfree(session);
-
-	return;
 }
 EXPORT_SYMBOL_GPL(l2tp_session_free);