[Quantization] import torch.fx only if torch.__version__ >= 1.8

wanchen.swc

2023-03-30 0438b966d6d9ef89fdd7a8d112d6e03b34122b1e

 egs/librispeech/conformer/conf/train_asr_conformer.yaml

@@ -69,7 +69,7 @@
dataset_conf:
    shuffle: True
    shuffle_conf:
        shuffle_size: 2048
        shuffle_size: 1024
        sort_size: 500
    batch_conf:
        batch_type: token