[clang] [llvm] [RISCV] Add processor definition and scheduling information for GR765 (PR #225638)

[Min-Yih Hsu via cfe-commits]

https://github.com/mshockwave commented:

Please split out the scheduling model part into a separate patch, and use NoSchedModel as a placeholder in the CPU definition in this patch.

https://github.com/llvm/llvm-project/pull/225638