[llvm] [RISCV] Remove CalleeSavedInfo for Zcmp/save-restore-libcalls registers (PR #79535)

[Visoiu Mistrih Francis via llvm-commits]

francisvm wrote:

> I'm going to attempt to register the slots with MFI.

that would be great, feel free to add me as a reviewer

https://github.com/llvm/llvm-project/pull/79535