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

[Mark Zhuang via cfe-commits]

zqb-all 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……

Yes，core is x60:  https://www.spacemit.com/spacemit-x60-core/

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