[clang] [clang][Sema] Emit warnings on incorrect AVR interrupt/signal handlers (PR #125328)

[Ben Shi via cfe-commits]

benshi001 wrote:

it is strange: I have added the case avkevl mentioned in my [repo](https://github.com/benshi001/llvm-project/commit/8ce75fc80b8bbfb79009e53c0d7ac8015983e4da), but this PR is not updated.

https://github.com/llvm/llvm-project/pull/125328