[llvm] [AMDGPU] SIMemoryLegalizer: Factor out check if memory operations can affect the global AS (PR #160129)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

### Merge activity

* **Sep 24, 11:20 AM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/160129).


https://github.com/llvm/llvm-project/pull/160129