Revert 1.43 and always make our own mapping of the Mostek chip. Trying to

Revert 1.43 and always make our own mapping of the Mostek chip. Trying to
reuse the prom mapping here is a bad idea because we alter its writeability
and the prom will not always expect this.

Repairs powerdown on Tapdole Ultrabook IIe.

discussed with and ok kettenis@