drm/nouveau/fb/tu102-: prepare for GSP-RM

- add (initial) R535 implementation of FB, need VRAM size etc for boot
- expose a way to "wrap" vram at a specific address/size as a standard
  nvkm_memory allocation, which will be used to write PTEs etc for RM-
  defined memory regions

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230918202149.4343-11-skeggsb@gmail.com