Drop -mllvm from the flag

Hopefully users can figure out they need to pass -mllvm on Clang

Author: lukel97

llvm/docs/ReleaseNotes.md

@@ -111,7 +111,7 @@ Changes to the RISC-V Backend
 
 * The loop vectorizer now performs tail folding by default on RISC-V, which
   removes the need for a scalar epilogue loop. To restore the previous behaviour
-  use `-mllvm -prefer-predicate-over-epilogue=scalar-epilogue`.
+  use `-prefer-predicate-over-epilogue=scalar-epilogue`.
 * `llvm-objdump` now has basic support for switching between disassembling code
   and data using mapping symbols such as `$x` and `$d`. Switching architectures
   using `$x` with an architecture string suffix is not yet supported.