[NETFILTER]: Clean up duplicate includes in net/netfilter/

This patch cleans up duplicate includes in
	net/netfilter/

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>