drm/nouveau/nvdec/r535: initial support

Adds support for allocating VIDEO_DECODER 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/20230918202149.4343-42-skeggsb@gmail.com