drm/nouveau/vfn/tu102-: support new-style interrupt tree

- switches ampere over now, and removes its hack mc implementation

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drm/nouveau/vfn: move NV_USERMODE class from host

- uses proper class IDs for Turing/Ampere

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drm/nouveau/vfn: add stub subdev for dev_func

Initially for NV_USERMODE class, and Turing/Ampere's new interrupt tree.

v2. fixup for ga103 early merge

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>