net: fec: reset fep link status in suspend function

On some i.MX6 serial boards, phy power and refrence clock are supplied
or controlled by SOC. When do suspend/resume test, the power and clock
are disabled, so phy device link down.

For current driver, fep->link is still up status, which cause extra operation
like below code. To avoid the dumy operation, we set fep->link to down when
phy device is real down.
...
if (fep->link) {
	napi_disable(&fep->napi);
	netif_tx_lock_bh(ndev);
	fec_stop(ndev);
	netif_tx_unlock_bh(ndev);
	napi_enable(&fep->napi);
	fep->link = phy_dev->link;
	status_change = 1;
}
...

Signed-off-by: Fugang Duan <B38611@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>