A device could have one of the following DMA attributes:
    * DMA not supported
    * DMA non-coherent
    * DMA coherent

So, this patch introduces enum dev_dma_attribute. This will be used by
new APIs introduced in later patches.
Signed-off-by: NSuravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NHanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>