drm/xe/guc: Don't allocate managed BO for each policy change

We shouldn't use xe_managed_bo_create_from_data() to allocate
temporary BO, as it will be released only on unload and every
change in wedge_mode policy will consume resources (including
precious GGTT). Instead just switchover to GuC buffer cache.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://lore.kernel.org/r/20250512220018.172-3-michal.wajdeczko@intel.com