drm/nouveau: initial pass at moving to struct nvif_device

This is an attempt at isolating some of the changes necessary to port
to NVIF in a separate commit.

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

drivers/gpu/drm/nouveau/nv04_fence.c

@@ -59,7 +59,7 @@ nv04_fence_sync(struct nouveau_fence *fence,
 static u32
 nv04_fence_read(struct nouveau_channel *chan)
 {
-	struct nouveau_fifo_chan *fifo = (void *)chan->object;
+	struct nouveau_fifo_chan *fifo = nvkm_fifo_chan(chan);;
 	return atomic_read(&fifo->refcnt);
 }