ucc_geth: Fix TX watchdog timeout handling

The timeout handling code is currently broken in several ways:

- It calls stop() (which frees all the memory and IRQ), and then
  calls startup() (which won't re-request IRQ, neither it will
  re-init the Fast UCC structure).
- It calls these routines from the softirq context, which is wrong,
  since stop() calls free_irq() (which might sleep) and startup()
  allocates things with GFP_KERNEL.
- It won't soft-reset the PHY. We need the PHY reset for at least
  MPC8360E-MDS boards with Marvell 88E1111 PHY, the PHY won't recover
  from timeouts w/o the reset.

So the patch fixes these problems by implementing the workqueue for the
timeout handling, and there we fully re-open the device via close() and
open() calls. The close/open paths do the right things, and I can see
that the driver actually survive the timeouts.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: David S. Miller <davem@davemloft.net>