sn32f2: inherit clocks from chibios

[dexter93]

We can now use the clocks definitions provided by ChibiOS. Take advantage of it and remove some hardcoded values. Switch System Timer from classic systick to tickless mode using the unused CT16B0 by default

needs SonixQMK/ChibiOS-Contrib#38

Description

Types of Changes

• [x] Core
• [ ] Bugfix
• [x] New feature
• [x] Enhancement/optimization
• [ ] Keyboard (addition or update)
• [ ] Keymap/layout/userspace (addition or update)
• [ ] Documentation

Issues Fixed or Closed by This PR

Checklist

• [ ] My code follows the code style of this project: C, Python
• [ ] I have read the PR Checklist document and have made the appropriate changes.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] I have tested the changes and verified that they work and don't break anything (as well as I can manage).