[media] omap3isp: stat: Merge dma_addr and iommu_addr fields

The fields store buffer addresses as seen from the device. The first one
is used with an external DMA engine while the second one is used with
the ISP DMA engine. As they're never used together, merge them.

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>