Avoid OOB in dynamic_keymap_reset

[zvecr]

Description

Various via keymaps are currently configured with incorrect amounts of keymap layers (45_ats:via, 10bleoledhub:via, etc).

Instead of a _Static_assert in keymap introspection to ensure keymap layers == dynamic keymap layer count....

• allow fewer keymap layers
  • will allow a small amount to be shaved off total firmware size
• most layers are "empty" anyway
  • why bother having to maintain 2+ layers full of _______

Types of Changes

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

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).