ppc64 iommu rewrite part 3/5

This one is probably too large for the list, sent privately to the usual culprits, lurkers can find it at:

http://gate.crashing.org/~benh/iommu-rewrite-part3.diff

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Bulk of the iommu rewrite.

Lots of things renamed, sillicaps killed, stuffs moved around and common code properly extracted from implementation specific code, new allocator, etc... The code is overall a lot simpler, faster, less prone to fail, and a lot more manageable.
I didn't use "bk mv", there is no need to keep the old history attached to the new file.