drm/xe: Call __guc_exec_queue_fini_async direct for KERNEL exec_queues

Usually we call __guc_exec_queue_fini_async via a worker as the
exec_queue fini can be done from within the GPU scheduler which creates
a circular dependency without a worker. Kernel exec_queues are fini'd at
driver unload (not from within the GPU scheduler) so it is safe to
directly call __guc_exec_queue_fini_async.

Suggested-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>