[clang] [llvm] [RISCV] Allow `Zicsr`/`Zifencei` to duplicate with `g` (PR #136842)

[Luke Lau via cfe-commits]

================
@@ -632,6 +632,8 @@ RISC-V Support
   Qualcomm's `Xqciint` extension to save and restore some GPRs in interrupt
   service routines.
 
+- `Zicsr` / `Zifencei` are allowed to duplicate with `g` in `-march`.
----------------
lukel97 wrote:

Nit
```suggestion
- `Zicsr` / `Zifencei` are allowed to be duplicated in the presence of `g` in `-march`.
```

https://github.com/llvm/llvm-project/pull/136842