Re: dma mask related fixups (including full bus_dma_mask support) v2

[Christoph Hellwig]

FYI, I've pulled this into the dma-mapping tree to make forward
progress.  All but oatch 4 had formal ACKs, and for that one Robin
was fine even without and explicit ack.  I'll also send a patch to
better document the zone selection as it confuses even well versed
people like Ben.