habanalabs: use single threaded WQ for event handling

Creating event queue workqueue using alloc_workqueue made it run in
multi threaded mode, which caused parallel dumping of events as well as
parallel events notifying to user, causing logs with multiple
events to be out of order.

Fixed by creating event queue workqueue as single threaded work queue.

Signed-off-by: Dani Liberman <dliberman@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>