Fix kernel panic when unload bh_threaded module

[xhorn-pan]

Ensuring the free_irq function properly releases IRQs for buttons, call free_irq() with button's device handler instead of NULL.

Summary by Bito

This pull request resolves a kernel panic issue by ensuring the free_irq function is called with the correct device handler when unloading the bh_threaded module. This enhancement improves the stability and reliability of IRQ management for button devices.

Unit tests added: False

Estimated effort to review (1-5, lower is better): 2 - The changes are straightforward and primarily focus on fixing a specific issue, making the review process relatively simple.

[jserv]

Use clang-format to ensure the consistent coding style.

[jserv]

You don't have to close and submit another pull request if you want to refine the commits. Instead, use git rebase -i and git push --force.

[xhorn-pan]

Little bit embarrassing, not clang-format but c-pointer problem.

[jserv]

Thank @xhorn-pan for contributing!

[xhorn-pan]

Thank you for writing and maintaining this book, I am learned a lot and still learning from it.