drm/xe: Kill the fbdev vma reuse hack

drm/xe: Kill the fbdev vma reuse hack

This fbdev vma reuse hacks is a massive layering violation. It
really does not belong in the fb pinning code. And it's in the
way of properly abstracting this stuff, so kill it.

I don't think this hack even does anything useful because the
normal view will just use bo->ggtt_node when present, and the
fbdev bo will be permanenly pinned with xe_bo_create_pin_map_at_novm()
which does set up bo->ggtt_node. So we should never end up
rebuilding the PTEs for the fbdev bo, even without the reuse hack.

v2: Pimp the commit message a a bit (Jani)
v3: Also nuke intel_fbdev_vma_pointer()

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20260508143426.26504-9-ville.syrjala@linux.intel.com