8139cp: fix missing napi_gro_flush.

The driver uses __napi_complete and napi_gro_receive. Without it, the
driver hits the BUG_ON(n->gro_list) assertion hard in __napi_complete.
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Tested-by: Marin Glibic <zhilla2@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/8139cp.c

@@ -563,6 +563,7 @@ static int cp_rx_poll(struct napi_struct *napi, int budget)
 		if (cpr16(IntrStatus) & cp_rx_intr_mask)
 			goto rx_status_loop;
 
+		napi_gro_flush(napi);
 		spin_lock_irqsave(&cp->lock, flags);
 		__napi_complete(napi);
 		cpw16_f(IntrMask, cp_intr_mask);