drm/nouveau/nvif: simplify and tidy library interfaces

A variety of tweaks to the NVIF library interfaces, mostly ripping out
things that turned out to be not so useful.

- Removed refcounting from nvif_object, callers are expected to not be
  stupid instead.
- nvif_client is directly reachable from anything derived from nvif_object,
  removing the need for heuristics to locate it
- _new() versions of interfaces, that allocate memory for the object
  they construct, have been removed.  The vast majority of callers used
  the embedded _init() interfaces.
- No longer storing constructor arguments (and the data returned from
  nvkm) inside nvif_object, it's more or less unused and just wastes
  memory.

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

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -1064,7 +1064,7 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int evict, bool intr,
 {
 	struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
 	struct nouveau_channel *chan = drm->ttm.chan;
-	struct nouveau_cli *cli = (void *)nvif_client(&chan->device->base);
+	struct nouveau_cli *cli = (void *)chan->user.client;
 	struct nouveau_fence *fence;
 	int ret;
 
@@ -1137,7 +1137,7 @@ nouveau_bo_move_init(struct nouveau_drm *drm)
 		if (chan == NULL)
 			continue;
 
-		ret = nvif_object_init(chan->object, NULL,
+		ret = nvif_object_init(&chan->user,
 				       mthd->oclass | (mthd->engine << 16),
 				       mthd->oclass, NULL, 0,
 				       &drm->ttm.copy);