[llvm] [LV] Apply urem folds to preheader (PR #213928)

[David Sherwood via llvm-commits]

david-arm wrote:

> The challenge with mass test updates is always reverting unwanted hunks :( If you use Magit or some other git frontend, it should make it easier?

Sorry, I don't know what you mean. How can I revert test changes if that would cause the tests to fail?

https://github.com/llvm/llvm-project/pull/213928