[llvm] [RISCV] Add hasSideEffects = true to ReadFRM (PR #139864)

[Gergely Futo via llvm-commits]

futog wrote:

> Do you have a case to show the miscompile?

Sure, here you go: https://godbolt.org/z/Kx1qsTeGY

https://github.com/llvm/llvm-project/pull/139864