[llvm] [RISCV][CFI] add function epilogue cfi information (PR #110810)

[Sam Elliott via llvm-commits]

https://github.com/lenary commented:

Nice update, I see the improvements!

I'm slightly confused as to why there sometimes is and sometimes is not any CFI information between a `cm.pop` and a `tail`/`ret`. I commented on one place where I saw this.

https://github.com/llvm/llvm-project/pull/110810