[clang] [clang][Sema] Move computing enum bits into a separate function (PR #126096)

[via cfe-commits]

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

Makes sense. Maybe wait a bit and see if anyone else has reservations about this, but from my point of view it’s fine as-is.

https://github.com/llvm/llvm-project/pull/126096