[llvm] LICM: extend hoistAddSub to unsigned case (PR #106373)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> or proofs it would be more useful to only prove the performed reassociation, without the loop, which is not really relevant here. It's easy to get false positive proofs when loops are involved.

Right, @fhahn taught me that in a different PR. Apparently, -src-unroll and -tgt-unroll are necessary. I've removed the proofs now.

https://github.com/llvm/llvm-project/pull/106373