vxge: transmit timeout deadlock

Use a workqueue to handle the device reset during a transmit timeout, as
there can be a deadlock during bringup.  Also, set the netif carrier off
before the watchdog reset is started to prevent the timeout from
reoccurring while still processing the first.

Signed-off-by: Jon Mason <jon.mason@exar.com>
Signed-off-by: Ram Vepa <ram.vepa@exar.com>
Signed-off-by: David S. Miller <davem@davemloft.net>