netfilter: Remove spurios included of netfilter.h

While testing my netfilter changes I noticed several files where
recompiling unncessarily because they unncessarily included
netfilter.h.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

drivers/net/wan/lapbether.c

@@ -40,7 +40,6 @@
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
 #include <linux/stat.h>
-#include <linux/netfilter.h>
 #include <linux/module.h>
 #include <linux/lapb.h>
 #include <linux/init.h>