[PATCH] dma-direct: take dma-ranges/offsets into account in resource mapping

[Christoph Hellwig]

I'd really like to hear something from the driver maintainers.  The
cod change itself looks fine, we just need to make sure it does not
break any driver assumptions.

And I think at least for the PCIe P2P and NTB cases I fear it might
break them.  The proper logic for those is in the p2p helpers, but
it seems like not everyone is using them.