drm/radeon: 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>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20190905070509.22407-5-kraxel@redhat.com

drivers/gpu/drm/radeon/radeon_ttm.c

@@ -794,7 +794,7 @@ int radeon_ttm_init(struct radeon_device *rdev)
 	r = ttm_bo_device_init(&rdev->mman.bdev,
 			       &radeon_bo_driver,
 			       rdev->ddev->anon_inode->i_mapping,
-			       NULL,
+			       rdev->ddev->vma_offset_manager,
 			       rdev->need_dma32);
 	if (r) {
 		DRM_ERROR("failed initializing buffer object driver(%d).\n", r);