habanalabs: Separate CS job completion from its deallocation

Current CS jobs are no longer needed after their completion.
However, jobs of future workload might be in use even after they are
completed. To allow that, the patch adds a refcount to the job object,
and decouples its completion handling from its deallocation.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>