drm/xe/guc: Add support for threshold KLVs in to_string() helper

Use MAKE_XE_GUC_KLV_THRESHOLDS_SET to generate missing conversion
of threshold KLV keys to string.

Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240514190015.2172-4-michal.wajdeczko@intel.com