netxen: remove netxen workqueue

o Remove private workqueue in the driver, move all
  scheduled tasks to keventd workqueues. This makes
  ports (interfaces) of same / different NIC boards
  independent, in terms of their link watchdog and
  reset tasks.

o Move quick checks for link status and temperature
  in timer callback, schedule watchdog task only if
  link status changed or temperature reached critical
  threshold.

This also fixes deadlock when thermal panic occurs,
watchdog work was flushing workqueue that it was
sitting on.

Signed-off-by: Amit Kumar Salecha <amit@qlogic.com>
Signed-off-by: Dhananjay Phadke <dhananjay@netxen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>