ucc_geth: Fix netdev watchdog triggering on suspend

Sometimes ucc_geth fails to suspend with the following trace:

 ucc_geth e0103000.ucc: suspend
 ucc_geth e0102000.ucc: suspend
 NETDEV WATCHDOG: eth0 (ucc_geth): transmit queue 0 timed out
 ------------[ cut here ]------------
 Badness at net/sched/sch_generic.c:255
 NIP: c021cb5c LR: c021cb5c CTR: c01ab4b4
 [...]
 NIP [c021cb5c] dev_watchdog+0x298/0x2a8
 LR [c021cb5c] dev_watchdog+0x298/0x2a8
 Call Trace:
 [c0389da0] [c021cb5c] dev_watchdog+0x298/0x2a8 (unreliable)
 [c0389e00] [c0031ed8] run_timer_softirq+0x16c/0x1dc
 [c0389e50] [c002c638] __do_softirq+0xa4/0x11c
 [...]

This patch fixes the issue by properly detaching the device on
suspend, and attaching it back on resume.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ucc_geth.c

@@ -3607,6 +3607,7 @@ static int ucc_geth_suspend(struct of_device *ofdev, pm_message_t state)
 	if (!netif_running(ndev))
 		return 0;
 
+	netif_device_detach(ndev);
 	napi_disable(&ugeth->napi);
 
 	/*
@@ -3665,7 +3666,7 @@ static int ucc_geth_resume(struct of_device *ofdev)
 	phy_start(ugeth->phydev);
 
 	napi_enable(&ugeth->napi);
-	netif_start_queue(ndev);
+	netif_device_attach(ndev);
 
 	return 0;
 }