[llvm] [LoopInterchange] Avoid using CacheCost if cache line size is zero (PR #126021)

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

I have misunderstood the logic of the CacheCost. It still makes sense even if the cache line size is 0.

https://github.com/llvm/llvm-project/pull/126021