[llvm] AMDGPU: Scratch instructions are trivially disjoint from SMEM and buffer instructions (PR #65287)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> LGTM. Perhaps even better would be to use address space checks (addrspacesMayAlias).

Part of the point of this is to avoid inspecting the MMO which isn't guaranteed to be there 

https://github.com/llvm/llvm-project/pull/65287