[llvm] [IR] Return correct memory effects for `convergencectrl` (PR #129874)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> Missing test update in instcombine/amdgpu? The patch I submitted a while ago had one of these leftover (the regression in [5c375c3](https://github.com/llvm/llvm-project/commit/5c375c3283fcd2bf4f98fe8627658e056e25dc44))

Rebased

https://github.com/llvm/llvm-project/pull/129874