drm/nouveau/fifo: audit and version fifo channel classes

The full object interfaces are about to be exposed to userspace, so we
need to check for any security-related issues and version the structs
to make it easier to handle any changes we may need in the future.

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

drivers/gpu/drm/nouveau/nouveau_chan.h

@@ -8,6 +8,8 @@ struct nouveau_channel {
 	struct nvif_device *device;
 	struct nouveau_drm *drm;
 
+	int chid;
+
 	struct nvif_object vram;
 	struct nvif_object gart;
 	struct nvif_object nvsw;