[llvm] LAA: rework and rename stripGetElementPtr (PR #125315)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> The title/description sound like this would just be updating comments ("clarify"), but the diff is code changes. If this is a refactoring/cleanup, please add NFC and update the title/description. It should start with what it is doing (the "Strip getGEPInductionOperand, rework and rename stripGetElementPtr" part), then elaborate the motivation for it.

I've updated the title, and the patch is not exactly a NFC, but I'm not sure it would be wise to add a test as @nikic is working on canonicalizing GEPs with variable offsets.

https://github.com/llvm/llvm-project/pull/125315