drm/xe/display: Avoid dereferencing xe_ggtt_node

drm/xe/display: Avoid dereferencing xe_ggtt_node

Start using xe_ggtt_node_addr, and avoid comparing the base offset
as vma->node is dynamically allocated.

Also sneak in a xe_bo_size() for stolen, too small to put as separate
commit.

Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patch.msgid.link/20260108101014.579906-13-dev@lankhorst.se