fix loss normalization for ddp training

haoneng.lhn

2023-12-08 acb9a0fec8d8a4dabeedcbb8e08c26f66d7083f0

ec8d197ce5b124e1b6f0d9ba0d9a7b9f1b7c0cd0 目录中不存在 ../../../egs/aishell/transformer/utils