[llvm] [LV] Don't ignore invariant stores when costing (PR #158682)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> Hmm, does that mean we now compute the cost of the scalar store for VF = 1, whereas before we would not compute it?

Yes, I think so.

https://github.com/llvm/llvm-project/pull/158682