i40e: lock service task correctly

i40e: lock service task correctly

The service task lock was being set in the scheduling function, not the
actual service task. This would potentially leave the bit set for a long
time before the task actually ran. Furthermore, if the service task
takes too long, it calls the schedule function to reschedule itself -
which would fail to take the lock and do nothing.

Instead, set and clear the lock bit in the service task itself. In the
process, get rid of the i40e_service_event_complete() function, which is
really just two lines of code that can be put right in the service task
itself.

Change-ID: I83155e682b686121e2897f4429eb7d3f7c669168
Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>