Fix the model test for pyhpc_equation_of_state.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