drm/xe/debugfs: Move sa_info from gt to tile directory

Our drm-based suballocator is implemented per-tile so it is better
to show its debug information also per-tile debugfs directory, not
under per-gt directory as it is done today.

To allow adding more per-tile attributes, prepare necessary helper
functions, like we already did for per-gt or per-uc attributes.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250829201106.1263-1-michal.wajdeczko@intel.com