update powerpc.git next and pull in some of benh's mmu patches

[Benjamin Herrenschmidt]

> Patches I want to still review and test:
> 
> 6/16 powerpc/mm: Split mmu_context handling v3
> 7/16 powerpc/mm: Rework context management for CPUs with no hash table  
> v2
> 9/16 powerpc/mm: Introduce MMU features v2
> 11/16 powerpc/mm: Add SMP support to no-hash TLB handling v3
> 12/16 powerpc/mm: Split low level tlb invalidate for nohash processors
> 14/16 powerpc/mm: Runtime allocation of mmu context maps for nohash  
> CPUs v2
> 15/16 powerpc/mm: Rework usage of _PAGE_COHERENT/NO_CACHE/GUARDED

New variants of the above coming. Note that pretty much any patch
touching cputable will break the mmu features patch, which is a pain to
fixup. The patch is based on -top- of the DCR stuff which touches
cputable, so please, Josh, review it asap so it can go in as a
pre-req :-)

Cheers,
Ben.