drm/xe/guc: Rename CONFIG_XE_LARGE_GUC_BUFFER

Rename XE_LARGE_GUC_BUFFER to XE_DEBUG_GUC to allow for more debug
only code (in subsequent patch) without adding more config defines
that each control only a single thing.

Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://lore.kernel.org/r/20250512215324.1457009-4-John.C.Harrison@Intel.com