Lock optimization in ENA
Handle IO interrupts using filter routine. That way, the main cleanup
task could be moved to the separate thread using taskqueue.
The deferred Rx cleanup task was removed, and now the cleanup task is
begin called instead. That way, the Rx lock could be removed.
In addition, Queue management (wake up and stop TX ring) was added, so
the TX cleanup task can be performed mostly lockless.
Submitted by: Michal Krawczyk <email@example.com>
Obtained from: Semihalf
Sponsored by: Amazon, Inc.