[clang] [llvm] [RISCV] Add Andes XAndesperf (Andes Performance) extension. (PR #135110)

[Kito Cheng via cfe-commits]

https://github.com/kito-cheng commented:

I am really happy to see this finally start to upstream as ex-Ande guy :P

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Do you have plan send PR to https://github.com/riscv-non-isa/riscv-toolchain-conventions?

https://github.com/llvm/llvm-project/pull/135110