[clang] [llvm] [RISCV] Add processor definition for Spacemit-K1 (PR #94564)

[Zhijin Zeng via cfe-commits]

zengdage wrote:

> Spacemit K1 is the name of the product/SoC or whatever you call it. The processor definitions in the RISCV backend are focusing on the CPU core. For Spacemit K1, the name of its core should be `X60`? I don't know……

@sunshaoce Hi, the `Spacemit-K1` is the SoC name and the cpu core name is `spacemit-x60`, so I suggest to use `spacemit-x60`.

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