iommu: msm: add iommu->dma_supported hook

iommu->dma_supported checks if the device can
support DMA to the memory described by the mask.
Add this for the legacy msm iommu driver.

Change-Id: Iebddc78cf1206bfed30c5d4e0f2ec01d012072e3
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>