[llvm] RISCV: Don't use MCTargetOptions::ABIName in the ELF target streamer (PR #224704)

[Jessica Clarke via llvm-commits]

jrtc27 wrote:

Treating it like we do -target(/-triple/-mtriple?) would seem sensible (especially with the "warn on override" part)

https://github.com/llvm/llvm-project/pull/224704