[llvm] [EarlyCSE] Fix improper icmp simplification (PR #122043)

[via llvm-commits]

llvmssh wrote:

> https://godbolt.org/z/59v83q7v7 If I don't miss something, there are no test changes after this patch. Can you provide an alive2 link to demonstrate that there is something wrong in `simplifyICmpInst`?

My case is not the same as the original, I will update it later.

https://github.com/llvm/llvm-project/pull/122043