skbuff: export skb_gro_receive

sctp GSO requires it and sctp can be compiled as a module, so we need to
export this function.

Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index f2b77e5..4724bcf 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3438,6 +3438,7 @@
 	NAPI_GRO_CB(skb)->same_flow = 1;
 	return 0;
 }
+EXPORT_SYMBOL_GPL(skb_gro_receive);
 
 void __init skb_init(void)
 {