drm/nouveau/disp/nv50-: skip DCB_OUTPUT_TV

We've never supported it.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Danilo Krummrich <me@dakr.org>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230919220442.202488-39-lyude@redhat.com