ixgbe: Update watchdog thread to accomodate longerlink_up events

This patch updates the link_up code and watchdog thread so that link_up
doesn't cause stack overflows due to long waits in interrupt context.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>