udp: remove stray export symbol

UDP GSO needs to export __udp_gso_segment to call it from ipv6.

I accidentally exported static ipv4 function __udp4_gso_segment.
Remove that EXPORT_SYMBOL_GPL.

Fixes: ee80d1ebe5ba ("udp: add udp gso")
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp_offload.c

@@ -247,7 +247,6 @@ static struct sk_buff *__udp4_gso_segment(struct sk_buff *gso_skb,
 				 udp_v4_check(sizeof(struct udphdr) + mss,
 					      iph->saddr, iph->daddr, 0));
 }
-EXPORT_SYMBOL_GPL(__udp4_gso_segment);
 
 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 					 netdev_features_t features)