drm/nouveau: switch to gem vma offset manager

Pass gem vma_offset_manager to ttm_bo_device_init(), so ttm uses it
instead of its own embedded struct.  This makes some gem functions
(specifically drm_gem_object_lookup) work on ttm objects.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20190905070509.22407-3-kraxel@redhat.com

drivers/gpu/drm/nouveau/nouveau_ttm.c

@@ -236,7 +236,7 @@ nouveau_ttm_init(struct nouveau_drm *drm)
 	ret = ttm_bo_device_init(&drm->ttm.bdev,
 				  &nouveau_bo_driver,
 				  dev->anon_inode->i_mapping,
-				 NULL,
+				  dev->vma_offset_manager,
 				  drm->client.mmu.dmabits <= 32 ? true : false);
 	if (ret) {
 		NV_ERROR(drm, "error initialising bo driver, %d\n", ret);