[llvm] [LV]: Improve accuracy of calculating remaining iterations of MainLoopVF (PR #156723)

[Hassnaa Hamdi via llvm-commits]

hassnaaHamdi wrote:

Sorry, I got confused about the SCEV patch. It handles the case when both TC and VF are vscale-based only.
So, this patch is still needed for handling the case of different numerical spaces.

https://github.com/llvm/llvm-project/pull/156723