[llvm] [RISCV] Support Parsing Nonstandard Relocations (PR #119909)

[Sam Elliott via llvm-commits]

lenary wrote:

Updated with the new relocation name from https://github.com/quic/riscv-elf-psabi-quic-extensions/commit/50f54da4e052f01ca3a1a555499ceac450e811a0 and included these names in the RISC-V elf relocation code enum so future code can be a bit clearer. 

https://github.com/llvm/llvm-project/pull/119909