netfilter: change generic l4 protocol number

0 is used by Hop-by-hop header and so this may cause confusion.
255 is stated as 'Reserved' by IANA.

Signed-off-by: Christoph Paasch <christoph.paasch@student.uclouvain.be>
Signed-off-by: Patrick McHardy <kaber@trash.net>

net/netfilter/nf_conntrack_proto_generic.c

@@ -92,7 +92,7 @@ static struct ctl_table generic_compat_sysctl_table[] = {
 struct nf_conntrack_l4proto nf_conntrack_l4proto_generic __read_mostly =
 {
 	.l3proto		= PF_UNSPEC,
-	.l4proto		= 0,
+	.l4proto		= 255,
 	.name			= "unknown",
 	.pkt_to_tuple		= generic_pkt_to_tuple,
 	.invert_tuple		= generic_invert_tuple,