[llvm] [LoopInterchange] Remove 'I' dependency (PR #140709)

[Ryotaro Kasuga via llvm-commits]

https://github.com/kasuga-fj commented:

> Is there any other case where the while-loop is executed other than `depends()` returning a non-`FullDependence` object?
>
> Maybe non-perfectly nested loops as in `reduction_03`? But those would be quite different cases, potentially we should query `isConfused()` to fill up the dependency matrix.

As far as I can tell, if the loops are perfectly nested, the while-loop isn't executed when a `FullDependence` object is returned. So using `isConfused()` seems more reasonable to me. Thanks for your advice, I'll fix to use that.

https://github.com/llvm/llvm-project/pull/140709