fix AttributeError: module 'onnx' has no attribute 'onnx'

[iysheng]

After I build tvm from souce code with guide.Then I do some test on pc with command as:

▸ python3.8 ~/Projects/ai_light_brain/npu_releate/tvm/thead/hhb_cli.py -S --model--S --model-file mobilenetv2-12.onnx --data-scale 0.017 --data-mean "124 117 104" --board x86
_ref --input-name "input" --output-name "output" --input-shape "1 3 224 224" --postprocess save_and_top5 --simulate-data persian_cat.jpg --quantization-scheme float16
[2023-12-05 21:01:42] (HHB LOG): Start import model.
Traceback (most recent call last):
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb_cli.py", line 21, in <module>
    main()
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb/main.py", line 559, in main
    sys.exit(_main(argv))
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb/main.py", line 553, in _main
    arg_manage.run_command(args_filter, curr_command_type)
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb/core/arguments_manage.py", line 1515, in run_command
    return args_filter.filtered_args.func(args_filter)
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb/core/main_command_manage.py", line 292, in driver_main_command
    mod, params = import_model(
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb/core/frontend_manage.py", line 417, in import_model
    mod, params = frontend.load(path, input_name, input_shape, output_name)
  File "/home/red/Projects/ai_light_brain/npu_releate/tvm/thead/hhb/core/frontend_manage.py", line 114, in load
    e = onnx.onnx.utils.Extractor(onnx_model)
AttributeError: module 'onnx' has no attribute 'onnx'

This pr just fix with this issue.

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