[clang] [llvm] [RISC-V] Add CSR read/write builtins (PR #85091)

[Jessica Clarke via cfe-commits]

jrtc27 wrote:

You can just use `({ ... })` to achieve that same goal with inline assembly (and write doesn't even need that, you can do it with a single statement). I'm not convinced the intrinsics gain you anything.

https://github.com/llvm/llvm-project/pull/85091