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

[Ryotaro Kasuga via llvm-commits]

kasuga-fj wrote:

@madhur13490 Could you please measure the compilation time impact? A quick test on my local showed improvements in several cases.

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