drm/xe: Make WA BB part of LRC BO

No idea why, but without this GuC context switches randomly fail when
running IGTs in a loop. Need to follow up why this fixes the
aforementioned issue but can live with a stable driver for now.

Fixes: 617d824c ("drm/xe: Add WA BB to capture active context utilization")
Cc: stable@vger.kernel.org
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Tested-by: Shuicheng Lin <shuicheng.lin@intel.com>
Link: https://lore.kernel.org/r/20250612031925.4009701-1-matthew.brost@intel.com