drm/nouveau/client: store default device by handle, not reference

Signed-off-by: Ben Skeggs <[e-mail]>

drivers/gpu/drm/nouveau/include/nvkm/core/client.h

···
 struct nvkm_client {
 	struct nvkm_namedb namedb;
 	struct nvkm_handle *root;
-	struct nvkm_device *device;
+	u64 device;
 	char name[32];
 	u32 debug;
 	struct nvkm_vm *vm;

drivers/gpu/drm/nouveau/nouveau_drm.c

···
 
 	dev->irq_enabled = false;
 	client = nvxx_client(&drm->client.base);
-	device = client->device;
+	device = nvkm_device_find(client->device);
 	drm_put_dev(dev);
 
 	nvkm_device_del(&device);

drivers/gpu/drm/nouveau/nvkm/core/client.c

···
 		nvkm_client_fini(client, false);
 		for (i = 0; i < ARRAY_SIZE(client->notify); i++)
 			nvkm_client_notify_del(client, i);
-		nvkm_object_ref(NULL, (struct nvkm_object **)&client->device);
 		nvkm_handle_destroy(client->root);
 		nvkm_namedb_destroy(&client->namedb);
 		*pclient = NULL;
···
 };
 
 int
-nvkm_client_new(const char *name, u64 devname, const char *cfg,
+nvkm_client_new(const char *name, u64 device, const char *cfg,
 		const char *dbg, struct nvkm_client **pclient)
 {
-	struct nvkm_device *device;
 	struct nvkm_client *client;
 	int ret;
-
-	device = nvkm_device_find(devname);
-	if (!device)
-		return -ENODEV;
 
 	ret = nvkm_namedb_create(NULL, NULL, &nvkm_client_oclass,
 				 NV_CLIENT_CLASS, nvkm_client_sclass,
···
 	/* prevent init/fini being called, os in in charge of this */
 	atomic_set(&nv_object(client)->usecount, 2);
 
-	nvkm_object_ref(&device->engine.subdev.object,
-			(struct nvkm_object **)&client->device);
+	client->device = device;
 	snprintf(client->name, sizeof(client->name), "%s", name);
 	client->debug = nvkm_dbgopt(dbg, "CLIENT");
 	return 0;

drivers/gpu/drm/nouveau/nvkm/engine/device/user.c

···
 		oclass = &nvkm_udevice_oclass_super;
 
 	/* find the device subdev that matches what the client requested */
-	device = client->device;
-	if (args->v0.device != ~0) {
+	if (args->v0.device != ~0)
 		device = nvkm_device_find(args->v0.device);
-		if (!device)
-			return -ENODEV;
-	}
+	else
+		device = nvkm_device_find(client->device);
+	if (!device)
+		return -ENODEV;
 
 	ret = nvkm_parent_create(parent, NULL, oclass, 0, nvkm_control_oclass,
 				 (1ULL << NVDEV_ENGINE_DMAOBJ) |