Prior to this commit, ownerboot had quite a lot of "magic addresses"
and flash chip layouts. This commit eliminates all of them.
All flash chip geometry is now computed from first principles and
two parameters:
1. The flash chip size
2. The number of images per chip (two means NORMAL/FALLBACK)
If (flash-chip-size / num-images) is too small, coreboot's build
process will notice this and fail.
It should be possible to build a single-image (i.e. no FALLBACK)
ownerboot for use on 8mbyte flash chips, which lets people try this
out without having to buy a new flash chip or (in the case of the
rk3399-gru-kevin laptop) doing any soldering.
At this point I am the only person who has contributed to ownerboot,
so I'm able to make this correction unilaterally. I wanted to do
this while I still had the chance.