This fixes a netdev watchdog timeout problem.
The software needs to call netif_tx_disable before running the
hardware calibration code. The problem condition can be shown by the
following timegraph.

|---5secs - ~10 jiffies time---|---|OOPS
^                              ^
last real TX                   periodic work stops netif

At OOPS, the following happens:
The watchdog timer triggers, because the timeout of 5secs
is over. The watchdog first checks for stopped TX.
_Usually_ TX is only stopped from the TX handler to indicate
a full TX queue. But this is different. We need to stop TX here,
regardless of the TX queue state. So the watchdog recognizes
the stopped device and assumes it is stopped due to full
TX queues (Which is a _wrong_ assumption in this case). It then
tests how far the last TX has been in the past. If it's more than
5secs (which is the case for low or no traffic), it will fire
a TX timeout.
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>