[PATCH] riscv: Clarify vlmax and length handling.

[Robin Dapp]

> It's somewhat common for mail clients to treat "--" as a signature 
> deliminator, it's "---" that git uses as a comment deliminator.

It's in my muscle memory somehow.  Always did it that way because I
didn't want the same delimiter as in the git part of the message.  Time 
to change that habit I suppose :) (or automate more of the process).