[clang] [llvm] [RISCV] Add MC layer support for Zicfiss. (PR #66043)

[Yeting Kuo via cfe-commits]

yetingk wrote:

Rebase but I didn't use alias to Zimop and Zcmop ways to achieve this code, since using them will lose some information like `Uses = [SSP]`. 

https://github.com/llvm/llvm-project/pull/66043