drm/nouveau/fifo: expose per-runlist CHID information

DRM uses this to setup fence-related items.

- nouveau_chan.runlist will always be "0" for the moment, not an issue
  as GPUs prior to ampere have system-wide channel IDs,

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