[llvm] [AMDGPU][Attributor] Remove final update of waves-per-eu after the attributor run (PR #155246)

[Shilei Tian via llvm-commits]

shiltian wrote:

> We do not need this in the attributor

Alternatively, if we don't want to have "bad" values here, we can still do a final touch after the attributor run, but this time only check if the existing attribute values match the one from `ST.getWavesPerEU`. If they don't, replace them.

https://github.com/llvm/llvm-project/pull/155246