The only unique thing about mip's sim_{read,write} helpers is the call to
address_translation on the incoming address. When we look closer at that
function though, we see it's just a stub that maps physical to virtual,
and the cache/return values are hardcoded. If we delete this function,
we can then collapse all the callers and drop the custom sim_{read,write}
logic entirely.
Some day we might want to add MMU support, but when we do, we'll want to
have the common layers handle things so all targets benefit.
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