[llvm] [AMDGPU][SDAG] Only fold flat offsets if they are inbounds PTRADDs (PR #165427)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

### Merge activity

* **Nov 19, 10:47 AM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.com/github/pr/llvm/llvm-project/165427).


https://github.com/llvm/llvm-project/pull/165427