drm/xe: Move hw_engine_fini to devm managed

Kernel BOs are destroyed with GGTT mappings, this is hardware
interaction so use devm.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240820172958.1095143-5-matthew.brost@intel.com