reserve legacy io regions on powermac

I think a great many drivers could be cleaned up by making IO fail if the proper IO address cookies haven't been obtained. This might be done with byteswapping, XOR, addition, putting a checksum in the top 2 bytes of a 64-bit cookie, or simply tracking where an ioremap has been done. Then the read and write operations can check this.

In general, make IO fail if a driver doesn't play by the rules.

Perhaps some of the low memory-mapped stuff on x86 could be moved.