igb: remove redundant timer updates and cleanup watchdog_task

igb: remove redundant timer updates and cleanup watchdog_task

The igb watchdog task is modifying the watchdog timer twice duing a single
run.  It only needs to be called once to reschedule itself for 2 seconds from
the last time it ran.

In addition I removed the allocation of the mac_info structure since it is
only called twice and is easier to access via the e1000_hw struct.

Signed-off-by: Alexander Duyck <[email protected]>
Signed-off-by: Jeff Kirsher <[email protected]>
Signed-off-by: David S. Miller <[email protected]>