iommu/arm-smmu: Implement .dma_supported()

The .dma_supported() checks to see if the device can support DMA to the
memory described by the mask.  Implement this for the arm-smmu driver.

Change-Id: Ie494d574b613c1c76e6f878048c74444dc25902c
Signed-off-by: Neeti Desai <neetid@codeaurora.org>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>