dma mask related fixups (including full bus_dma_mask support) v2

[Benjamin Herrenschmidt]

On Mon, 2018-10-01 at 16:32 +0200, Christoph Hellwig wrote:
> 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.

Thanks. I"ll try to dig out some older systems to test.

Cheers,
Ben.