[llvm] AMDGPU: Add a subtarget feature for fine-grained remote memory support (PR #96442)

[Matt Arsenault via llvm-commits]

arsenm wrote:

### Merge activity

* **Jul 10, 8:37 AM EDT**: @arsenm started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/96442).


https://github.com/llvm/llvm-project/pull/96442