[llvm] [RISCV] Renaming muladdi to muliadd as per v0.5 spec. NFC (PR #124237)

[Sam Elliott via llvm-commits]

lenary wrote:

Please can you check the extension version in LLVM is still correct, and if not update it (including the docs and release notes)

This is not NFC either, so fix the PR title :) 

https://github.com/llvm/llvm-project/pull/124237