drm/xe/configfs: Drop trailing semicolons

Drop the semicolons from the dummy implementation: they shouldn't be
there.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20250528-engine-mask-v4-1-f4636d2a890a@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>