[NETFILTER]: nf_conntrack: mark protocols __read_mostly

Also remove two unnecessary EXPORT_SYMBOLs and move the
nf_conntrack_l3proto_ipv4 declaration to the correct file.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
index 0fca7e8..ab154fb 100644
--- a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
@@ -276,7 +276,7 @@
 };
 #endif /* CONFIG_SYSCTL */
 
-struct nf_conntrack_l4proto nf_conntrack_l4proto_icmpv6 =
+struct nf_conntrack_l4proto nf_conntrack_l4proto_icmpv6 __read_mostly =
 {
 	.l3proto		= PF_INET6,
 	.l4proto		= IPPROTO_ICMPV6,
@@ -297,5 +297,3 @@
 	.ctl_table		= icmpv6_sysctl_table,
 #endif
 };
-
-EXPORT_SYMBOL(nf_conntrack_l4proto_icmpv6);