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

- (temporarily) disable if GSP-RM detected, will be added later
- move BAR2 teardown from dtor(), it doesn't belong there

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230918202149.4343-7-skeggsb@gmail.com