drm/xe/bo: Add xe_bo_has_valid_ccs_bb helper

This will allow as to drop ugly IS_VF_CCS_BB_VALID macro.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Link: https://lore.kernel.org/r/20250908123025.747-6-michal.wajdeczko@intel.com