DMA-buf P2P

[Christian König]

Hi guys,

as promised this is the patch set which enables P2P buffer sharing with DMA-buf.

Basic idea is that importers can set a flag noting that they can deal with and sgt which doesn't contains pages.

This in turn is the signal to the exporter that we don't need to move a buffer to system memory any more when a remote device wants to access it.

Please review and/or comment,
Christian.