[clang] [llvm] [RISCV] Add support for Ziccid 1.0 (PR #196459)

[Sam Elliott via llvm-commits]

https://github.com/lenary approved this pull request.

Extensions without instructions are reasonably easy.

I'm happy with the implementation, and Ziccif is landed, so I think this is all ok?

Do wait for other reviewers.

https://github.com/llvm/llvm-project/pull/196459