[llvm] [RISCV]Add Sm1p13、Ss1p13 extensions (PR #121634)

[via llvm-commits]

dong-miao wrote:

> The commit message is rather lacking specifics; especially "[RISCV]Update CSRs" is (a) badly formatted (b) too terse and vague. Since this is just for RV32 [mh]edelegh CSRs, it would be appropriate to mention that explicitly.
I made the corresponding changes.


https://github.com/llvm/llvm-project/pull/121634