[coreboot] BIOS region alignment on ivybridge platforms.

[persmule]

Hi Nicola Corna and Marek Behun,

I have reported that a coreboot image with a cleansed and truncated ME
region may cause the first boot costing more than 5 minutes
(https://mail.coreboot.org/pipermail/coreboot/2017-April/084004.html).
Now I confirm that in order to prevent this, the bios region should be
aligned to 64KiB (0x10000) on ivybridges. Sandybridges do not have such
limitation.

Persmule