Fix softmax parsing in pytorch and add test

[JanFSchulte]

Fixes issues with softmax activation in pytorch parser reported in https://github.com/fastmachinelearning/hls4ml/issues/1083 and adds softmax activation to the pytest.

I also added a one-line change to fix https://github.com/fastmachinelearning/hls4ml/issues/1074 while I'm messing with the pytorch parser.

Type of change

• [x] Bug fix (non-breaking change that fixes an issue)

Tests

Added softmax to the pytest, where it works now.

Test Configuration:

Checklist

• [x] I have read the guidelines for contributing.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [x] I have installed and run pre-commit on the files I edited or added.
• [x] I have added tests that prove my fix is effective or that my feature works.