drm/xe: Ensure LR engines are not persistent

With our ref counting scheme long running (LR) engines only close
properly if not persistent, ensure that LR engines are non-persistent.

v2: spell out LR

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>