e1000: use work queues

E1000 is using several timers that in a follow on patch
will need to acquire the rtnl_lock in order to be safe.

This patch moves the timer bodies into work queues which
will allow the next patch to add rtnl_lock.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>