[llvm] [IR][RISCV] Remove @llvm.experimental.vp.splat (PR #171084)

[Min-Yih Hsu via llvm-commits]

https://github.com/mshockwave commented:

> Do we need to add AutoUpgrade support for compatibility with old bitcode?

If we are to add this AutoUpgrade, what would we substitute the scalable vector version of this intrinsic with? I can only think of replacing it with store + zero-stride load, or multiple layers of vector.interleave

https://github.com/llvm/llvm-project/pull/171084