Improve Adafruit BLE configuration defines

[fauxpark]

Description

By convention these defines should be in SCREAMING_SNAKE_CASE.

The frequency define has been changed to ADAFRUIT_BLE_SCK_DIVISOR as there is no F_CPU equivalent for ARM, so it cannot be easily calculated automatically. It defaults to 2, the value it would be for a Feather 32U4 running at 8MHz with a 4MHz SPI clock speed. ARM users will likely always need to increase this as those chips run at much higher speeds, and even with the /2 division, the BLE module probably won't be able to keep up.

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).

[Duckle29]

LGTM