[llvm] [RISCV][NFC] Simplify RISCVInstrInfo::copyPhysReg (PR #84139)

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

Why is this not just a loop over an array of triples? Macros should be avoided in C++ where possible, and they’re not needed here.

https://github.com/llvm/llvm-project/pull/84139