[llvm] [RISCV] Simplify fixup kinds that force relocations (PR #136088)

[Sam Elliott via llvm-commits]

lenary wrote:

If you can obtain some problematic MIR with `-stop-before=asm-printer` or similar, that would be very helpful. You should only need it for one object.

https://github.com/llvm/llvm-project/pull/136088