[llvm] [RISCV][NFC] Refactor Vendor Reloc Declarations (PR #138226)

[Sudharsan Veeravalli via llvm-commits]

https://github.com/svs-quic approved this pull request.

LGTM!

A more general question - is there a reason you call it nonstandard_reloc and not vendor_reloc? Can there be other types of non_standard relocations apart from the vendor ones?

https://github.com/llvm/llvm-project/pull/138226