[llvm] [RISCV] Use experimental.vp.splat to splat specific vector length elements. (PR #101329)

[Luke Lau via llvm-commits]

lukel97 wrote:

Oh woops I missed the comments above about the pointer type crash. In that case then I think we should backport this  given that #98579 is in. Since this is independent of whether or not RISCVGatherScatterLowering emits vp_strided_load

https://github.com/llvm/llvm-project/pull/101329