drm/xe/vf: Don't expose privileged GT debugfs files if VF

Some of the debugfs files require access to the registers that are
not accessible to the VFs. Don't expose those files on VF drivers.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Tested-by: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
Reviewed-by: Marcin Bernatowicz <marcin.bernatowicz@linux.intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://lore.kernel.org/r/20250403142635.1821-4-michal.wajdeczko@intel.com