Fix CRC for AVR and enable again.

[daskygit]

I don't really understand the implications of QUANTUM_LIB_SRC vs SRC.

I noticed removing the weak attribute on crc_init() threw up a undefined error in keyboard.c, so assumed it wasn't getting included correctly.

I've flashed this on a spare promicro and it seems to work correctly with the crkbd and kyria default keymaps. Might be good for someone else to confirm.

Description

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).

[drashna]

I don't really understand the implications of QUANTUM_LIB_SRC vs SRC.

QUANTUM_LIB_SRC is added separately, and later in the compilation process, doesn't get optimization applied to it, and can be compiled out completely, if not needed. IIRC.

Usually, it's best to use SRC, unless there are timing issues or weird behavior, especially with LTO enabled.