[llvm] [LV] Create in-loop sub reductions (PR #147026)

[Sander de Smalen via llvm-commits]

https://github.com/sdesmalen-arm commented:

Thanks for adding `AddChainWithSubs`, this avoids any possible confusing arising from new code not realising that `sub` might also be one of the operands in the chain, requiring negating the inputs.

https://github.com/llvm/llvm-project/pull/147026