gianfar:don't add FCB length to hard_header_len

FCB(Frame Control Block) isn't the part of netdev hard header.
Add FCB to hard_header_len will make GRO fail at MAC comparision stage.
Signed-off-by: Jiajun Wu <b06378@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/gianfar.c

@@ -1082,7 +1082,7 @@ static int gfar_probe(struct platform_device *ofdev)
 
 	if (dev->features & NETIF_F_IP_CSUM ||
 			priv->device_flags & FSL_GIANFAR_DEV_HAS_TIMER)
-		dev->hard_header_len += GMAC_FCB_LEN;
+		dev->needed_headroom = GMAC_FCB_LEN;
 
 	/* Program the isrg regs only if number of grps > 1 */
 	if (priv->num_grps > 1) {