Add supports for the port unlink(s) eventdev entry points.
The unlink operation is an asynchronous operation executed by
a control thread, and the unlinks-in-progress function reads
a counter shared with the control thread.
Signed-off-by: Timothy McDaniel <timothy.mcdaniel@intel.com>
Reviewed-by: Gage Eads <gage.eads@intel.com>