[llvm] [RISCV] Add scheduler definitions for SpacemiT-X60 (PR #137343)

[Mark Zhuang via llvm-commits]

zqb-all wrote:

> I just wonder why we didn't ask Spacemit guys to provide the schedule model. They have a compiler team but are not so active in upstream.
> 
> cc @zqb-all @zengdage @sunshaoce 

Thanks Mikhail for bringing the initial schedule model support to x60. We will take a look at this patch and work with the upstream to improve the performance of x60.

https://github.com/llvm/llvm-project/pull/137343