netfilter: nf_nat_ipv4: remove obsolete EXPORT_SYMBOL

There are no external callers anymore, previous change just
forgot to also remove the EXPORT_SYMBOL().

Fixes: 9971a514 ("netfilter: nf_nat: add nat type hooks to nat core")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/nf_nat_l3proto_ipv4.c

@@ -264,7 +264,6 @@ nf_nat_ipv4_fn(void *priv, struct sk_buff *skb,
 
 	return nf_nat_inet_fn(priv, skb, state);
 }
-EXPORT_SYMBOL_GPL(nf_nat_ipv4_fn);
 
 static unsigned int
 nf_nat_ipv4_in(void *priv, struct sk_buff *skb,