[clang] [llvm] [RISCV] Add processor definition for XiangShan-KunMingHu-V2R2 (PR #123193)

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liliumShade wrote:

> LGTM in general, but I have a question here: can you clarify the naming strategy? The name used in `-mcpu` is `xiangshan-kunminghu`, which corresponds to the `V2R2` version now apparently. Then, will there be `V2R3`/`V3R2`/...? If so, what should we use in `-mcpu`?
  
Thank you for raising this! To clarify: V2R2 is the current frozen version of kunminghu, the subsequent development in the plan will not affect the ISA string and pipeline.

If significant changes ever arise in a future major version (e.g., a hypothetical V3), we will introduce a new -mcpu name to reflect that divergence. 

https://github.com/llvm/llvm-project/pull/123193