[llvm] [RISCV]Add support for resolving encoding conflicts among vendor specific CSRs (PR #96174)

[Ana Pazos via llvm-commits]

apazos wrote:

Sounds good, @topperc!

@quic-garvgupt,  please have a follow up patch that will set the vars to true for RISC-V target.

https://github.com/llvm/llvm-project/pull/96174