[llvm] [BOLT][NFC] Refactor function state check (PR #73420)

[Amir Ayupov via llvm-commits]

https://github.com/aaupov approved this pull request.

Just for my understanding: we were testing the conditions used for emission rather than the actual emitted state of BF, and this diff fixes it, right? 
Which cases did we miss where the function was simple but wasn't emitted?

https://github.com/llvm/llvm-project/pull/73420