[llvm] [RISCV][NFC] Replace reportError wrappers with direct reportFatalUsageError calls (PR #148142)

[Sam Elliott via llvm-commits]

lenary wrote:

@nosba0957 please can you make your email public: https://llvm.org/docs/DeveloperPolicy.html#github-email-address

Once you do so, I can land this for you.

https://github.com/llvm/llvm-project/pull/148142