[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/ipv4/netfilter/nf_conntrack_proto_icmp.c b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
index f965733..6593fd2 100644
--- a/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
+++ b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
@@ -312,7 +312,7 @@
 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 #endif /* CONFIG_SYSCTL */
 
-struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp =
+struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
 {
 	.l3proto		= PF_INET,
 	.l4proto		= IPPROTO_ICMP,
@@ -338,4 +338,3 @@
 #endif
 #endif
 };
-EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_icmp);