Docs needed: fire updates

[lifang0209]

What sort(s) of documentation issue is this?

• [x] Something is missing.
• [x] Something is (or might be) incorrect or outdated.
• [ ] Something is confusing.
• [ ] Something is broken.

What part(s) of the documentation does this concern?

• [x] Technical Note (science and design of the model)
• [ ] User's Guide (using the model and related tools)
• [ ] Somewhere else (e.g., README file, tool help text, or code comment): Please specify
• [ ] I don't know

Describe the issue

A clear and concise description of what is missing or wrong. I need to update the equations, numbers in a table, and several text lines in the Tech Note to reflect the fire model updates for CLM6.