[llvm] [LV] Support strided load with a stride of -1 (PR #128718)

[Mel Chen via llvm-commits]

Mel-Chen wrote:

@fhahn Ping, I extended VPVectorPointerRecipe to achieve the goal for now. If you think we should introduce a new pointer recipe instead, please let me know.
746caaed4093590a2419823c4f71e3a51e99b382

https://github.com/llvm/llvm-project/pull/128718