drm/xe: Use ttm_bo_access in xe_vm_snapshot_capture_delayed

drm/xe: Use ttm_bo_access in xe_vm_snapshot_capture_delayed

Non-contiguous mapping of BO in VRAM doesn't work, use ttm_bo_access
instead.

v2:
 - Fix error handling

Fixes: 0eb2a18a8fad ("drm/xe: Implement VM snapshot support for BO's and userptr")
Suggested-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241126174615.2665852-7-matthew.brost@intel.com