[media] omap3isp: stat: Use the DMA API

Replace the OMAP-specific IOMMU API usage by the DMA API. All buffers
are now allocated using dma_alloc_coherent() and the related sg table is
retrieved using dma_get_sgtable() for sync operations.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>