[llvm] [GlobalIsel][AArch64] legalize ptr add (PR #89218)

[Dhruv Chawla via llvm-commits]

dc03-work wrote:

> After this patch, it still asserts.

You can likely put a `moreElementsToNextPow2` before the `clampNumElements` to address this.

https://github.com/llvm/llvm-project/pull/89218