[clang] [llvm] [RISCV] Add processor definition for SpacemiT-X60 (PR #94564)

[Shao-Ce SUN via llvm-commits]

sunshaoce wrote:

> Could you explain these numbers? It looks like data in some columns is missing.

I only ran the default `base metrics` once. The geometric mean of this  `Estimated Base Ratio`  column can be regarded as the comprehensive score for this item.
[Q14. What is the difference between a "base" metric and a "peak" metric?](https://www.spec.org/cpu2006/docs/readme1st.html#Q14)

https://github.com/llvm/llvm-project/pull/94564