[coreboot] ARMv8 MMU changes

[Julius Werner]

Hi Patrick et. al.,

Continuing from what you said on IRC, let's please discuss this before you
spend time to work on any major changes to the ARMv8 MMU code. I don't
think that should be necessary (especially changing the GRANULE_SIZE which
is a complication I'd really like to avoid having), and I'd like to
understand what you're trying to do first. Can you explain what memory
ranges you need to map on your SoC and why they need to be so large?

Thanks,
Julius