drm/xe: Add performance tunings to debugfs

Add a list of active tunings to debugfs, analogous to the existing
list of workarounds.

Rationale being that it seems to make sense to either have both or none.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250227101304.46660-6-tvrtko.ursulin@igalia.com


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