Free running timer

[secworks]

Description

This PR implements a change to the existing timer to add a free running mode. This is currently an initial version. The testbenches has not been updated with tests of the new mode. But it builds and allow us to measure the amount of resources the changes cause.

Note that this PR breaks the behavior of the timer. Previously both the timer and the prescaler would count down from a set value. The PR changes this so that now the timer and prescaler starts at zero and counts up to the set values. Applications that look at the timer current_value will probably be confused. Applications that just sets the timer and wait for it to complete (stop running) will not be affected.

Fixes #252

Type of change

Please tick any that are relevant to this PR and remove any that aren't.

• [ ] Bugfix (non breaking change which resolve an issue)
• [ ] Feature (non breaking change which adds functionality)
• [X] Breaking Change (a change which would cause existing functionality to not work as expected)
• [ ] Documentation (a change to documentation)

Submission checklist

• [X] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my changes
• [ ] I have tested and verified my changes on target
• [ ] My changes are well written and CI is passing
• [ ] I have squashed my work to relevant commits and rebased on main for linear history
• [ ] I have added a "Co-authored-by: x" if several people contributed, either pair programming or by squashing commits from different authors.
• [ ] I have updated the documentation where relevant (readme, dev.tillitis.se etc.)
• [ ] QEMU is updated to reflect changes