drm/xe/vf: Shadow buffer management for CCS read/write operations

drm/xe/vf: Shadow buffer management for CCS read/write operations

CCS copy command consist of 5-dword sequence. If vCPU halts during
save/restore operations while these sequences are being programmed,
incomplete writes can cause page faults during IGPU CCS metadata saving.

Use shadow buffer management to prevent partial write issues during CCS
operations.

Signed-off-by: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20251118120745.3460172-3-satyanarayana.k.v.p@intel.com