[llvm] TargetTransformInfo: Add missing consts to a couple of methods (PR #128492)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Feb 24, 7:06 AM EST**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/128492).


https://github.com/llvm/llvm-project/pull/128492