drm/xe: fix stale comment about unordered_wq usage

Display has switched to its own workqueue, no longer using
xe->unordered_wq.

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250731111214.1130130-1-jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>