v4l2: expose memory:DMABuf capsfeature
Submitted by Gwenole Beauchesne @gb
Link to original bug (#745459)
Description
This is a follow-up to bug 743345 where it became apparent that some memory:dmabuf capsfeature could be useful for both negotiation purposes, but also probable optimization wins.
Though, the initial intent here is only to help negotiation of elements.