[llvm] [IPO] Added attributor for identifying invariant loads (PR #141800)

[via llvm-commits]

zGoldthorpe wrote:

@krzysz00 Since it was small, I decided to add it in. It at least works for `llvm.admgcn.make.buffer.rsrc.p7.p1`, now.

https://github.com/llvm/llvm-project/pull/141800