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 <[e-mail]>
Reviewed-by: Daniel Vetter <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/nouveau/nouveau_ttm.c

···
 	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);