[llvm] [RISCV] Initial codegen support for the XRivosVizip extension (PR #131933)

[Min-Yih Hsu via llvm-commits]

https://github.com/mshockwave commented:

We probably can use this for `llvm.vector.(de)interleave2` and other power-of-two factors as well. But that can be a follow-up patch.

https://github.com/llvm/llvm-project/pull/131933