drm/nouveau/ofa/r535: initial support

Adds support for allocating OFA classes from RM.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230918202149.4343-45-skeggsb@gmail.com