ixgbevf: combine all of the tasks into a single service task

This change combines the reset and watchdog tasklets into a single task.

The advantage of this is that we can avoid multiple schedules of the reset
task when we have a reset event needed due to either the mailbox going down
or transmit packets being present on a link down.

CC: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>