[llvm] [SimplifyCFG] Fix weight calculation for `simplifySwitchOfPowersOfTwo` (PR #165956)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

### Merge activity

* **Nov 5, 8:01 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.com/github/pr/llvm/llvm-project/165956).


https://github.com/llvm/llvm-project/pull/165956