Model support for yolov3 with Torch_XLA2

[ManfeiBai]

Fix the model test for yolov3.py

1. setup env according to Run a model under torch_xla2
2. Run model test under run_torchbench/ with python models/your_target_model_name.py
3. Fix the failure.

Please refer to
this guide as guide to fix:

Also refer to these PRs:

• Add documentation on fixing a torchbench model on torchxla2 #7583

[ManfeiBai]

cc @tracych477, this issue would be the first model issue to try, please feel free to reply in this issue, so that we could assign it to you

[tracych477]

Thanks Manfei! Feel free to assign it to me.