drm/xe: don't expose the GSCCS to users

The kernel is the only expected user of the GSCCS, so we don't want to
expose it to userspace.

Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230817201831.1583172-7-daniele.ceraolospurio@intel.com


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>