[clang] [clang][RISCV] Support RVV bfloat16 C intrinsics (PR #89354)

[Kito Cheng via cfe-commits]

kito-cheng wrote:

> Oh, I forgot to remove them. Or do you think they should be moved to bfloat folder to make them consistent?

Remove files from this PR, that should be a separated NFC PR for moving those files, but I am fine to keep those file in same place :)

https://github.com/llvm/llvm-project/pull/89354