drm/ttm: nuke invalidate_caches callback

Another completely unused feature.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Link: https://patchwork.freedesktop.org/patch/348265/

drivers/gpu/drm/ttm/ttm_bo.c

@@ -372,14 +372,7 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
 	}
 
 moved:
-	if (bo->evicted) {
-		if (bdev->driver->invalidate_caches) {
-			ret = bdev->driver->invalidate_caches(bdev, bo->mem.placement);
-			if (ret)
-				pr_err("Can not flush read caches\n");
-		}
-		bo->evicted = false;
-	}
+	bo->evicted = false;
 
 	if (bo->mem.mm_node)
 		bo->offset = (bo->mem.start << PAGE_SHIFT) +