gianfar: Make reset_gfar static

Fix sparse warning:

drivers/net/ethernet/freescale/gianfar.c:2070:6:
 warning: symbol 'reset_gfar' was not declared. Should it be static?
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/gianfar.c

@@ -2067,7 +2067,7 @@ static int gfar_change_mtu(struct net_device *dev, int new_mtu)
 	return 0;
 }
 
-void reset_gfar(struct net_device *ndev)
+static void reset_gfar(struct net_device *ndev)
 {
 	struct gfar_private *priv = netdev_priv(ndev);