net/fec: improve pm for better suspend/resume

The following commit made a fix to use fec_enet_open/fec_enet_close
over fec_enet_init/fec_stop for suspend/resume, because fec_enet_init
does not allow to have a working network interface at resume.

  e3fe8558c7fc182972c3d947d88744482111f304
  net/fec: fix pm to survive to suspend/resume

This fix works for i.mx/mxc fec controller, but fails on mx28 fec
which gets a different interrupt logic design. On i.mx fec, interrupt
can be triggered even bit ETHER_EN of ECR register is not set. But
on mx28 fec, ETHER_EN must be set to get interrupt work. Meanwhile,
MII interrupt is mandatory to resume the driver, because MDIO
read/write changed to interrupt mode by commit below.

  97b72e4320a9aaa4a7f1592ee7d2da7e2c9bd349
  fec: use interrupt for MDIO completion indication

fec_restart/fec_stop comes out as the solution working for both
cases.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/fec.c

@@ -1372,8 +1372,10 @@ fec_suspend(struct device *dev)
 
 	if (ndev) {
 		fep = netdev_priv(ndev);
-		if (netif_running(ndev))
-			fec_enet_close(ndev);
+		if (netif_running(ndev)) {
+			fec_stop(ndev);
+			netif_device_detach(ndev);
+		}
 		clk_disable(fep->clk);
 	}
 	return 0;
@@ -1388,8 +1390,10 @@ fec_resume(struct device *dev)
 	if (ndev) {
 		fep = netdev_priv(ndev);
 		clk_enable(fep->clk);
-		if (netif_running(ndev))
-			fec_enet_open(ndev);
+		if (netif_running(ndev)) {
+			fec_restart(ndev, fep->full_duplex);
+			netif_device_attach(ndev);
+		}
 	}
 	return 0;
 }