[NETFILTER]: convert nfmark and conntrack mark to 32bit

As discussed at netconf'05, we convert nfmark and conntrack-mark to be
32bits even on 64bit architectures.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 948527e..2e40f4c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -259,7 +259,7 @@
 
 	void			(*destructor)(struct sk_buff *skb);
 #ifdef CONFIG_NETFILTER
-	unsigned long		nfmark;
+	__u32			nfmark;
 	__u32			nfcache;
 	__u32			nfctinfo;
 	struct nf_conntrack	*nfct;