drm/xe: Convert xe_fb_pin to use a callback for insertion into GGTT

drm/xe: Convert xe_fb_pin to use a callback for insertion into GGTT

The rotation details belong in xe_fb_pin.c, while the operations involving
GGTT belong to xe_ggtt.c. As directly locking xe_ggtt etc results in
exposing all of xe_ggtt details anyway, create a special function that
allocates a ggtt_node, and allow display to populate it using a callback
as a compromise.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Link: https://patch.msgid.link/20260108101014.579906-11-dev@lankhorst.se