Incorrect behaviour with INT_MAX pmpaddr

[Timmmm]

If you set pmpaddr to ones() then it will misbehave. For NAPOT it will return (zeros(), zeros()). For NA4 it will return (ones(), zeros()). In both cases it will match no addresses, whereas it should match all memory, or the top 4 bytes respectively.

I have a fix for this, and a test (I know!). The test is written in Zig... I was experimenting with that. I'll demo it in the next meeting I'm at (24th).