net: do not export skb_gro_receive()

skb_gro_receive() is only called from tcp_gro_receive() which is
not in a module.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/skbuff.c

@@ -3244,7 +3244,6 @@ done:
 	NAPI_GRO_CB(skb)->same_flow = 1;
 	return 0;
 }
-EXPORT_SYMBOL_GPL(skb_gro_receive);
 
 void __init skb_init(void)
 {