fec: Invert the order of function calls in fec_restart()

commit 54309fa6 ("net: fec: fix kernel oops when plug/unplug cable many times")
introduced the following 'if' block in the beginning of fec_start():

	if (netif_running(ndev)) {
		netif_device_detach(ndev);
		napi_disable(&fep->napi);
		netif_stop_queue(ndev);
		netif_tx_lock_bh(ndev);
	}

Then later in the end of fec_restart() there is another block that calls the
opposite of each one of these functions.

The correct approach would be to also call them with in the reverse order, so
that we have as result:

	if (netif_running(ndev)) {
		netif_tx_unlock_bh(ndev);
		netif_wake_queue(ndev);
		napi_enable(&fep->napi);
		netif_device_attach(ndev);
	}

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>