[coreboot] cbfs fix

[Myles Watson]

This fixes the boot for CBFS with the s2895.  As an added bonus it
still works on serengeti :)

The problem was that the master cbfs record was located at the end of
the flash and overwrote anything that was there.  Luckily for most
targets this wasn't a problem, but for ck804 or mcp55-based machines
it overwrote the romstrap.

The fix is simple:
1. Put the master cbfs record above the bootblock instead of on it.

There are many improvements that can be made to cbfs, but for now I
think this improves the situation substantially.

Signed-off-by: Myles Watson

Thanks,
Myles