LED drivers: misc formatting and typos

[fauxpark]

Description

• Tightened up/normalised formatting
• Added missing license headers
• 3218: tweaked set_value()/set_color() to match the rest of the drivers - fixes potential out of bounds
• 3737: typo in IS31FL3737_CS_PULLDOWN
• snled27351: fixed wrong dirty flag being used in update_pwm_buffers()
• Moved some dirty flag assignments inside their checks (as there is no point setting them if it's the same value)

Types of Changes

• Core
• Bugfix
• New feature
• 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).