Added an __init__.py for hi6200 agent

[mjrand]

Description

Added a blank __init__.py file to the hi6200 folder in socs.agents.

Motivation and Context

The agent couldn't start without this file and it was not added in the original PR.

How Has This Been Tested?

Has not been tested. Minimal chance to make hi6200 agent work less than it currently is.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.