powerpc: Change archdata dma_data to a union

Sometimes this is used to hold a simple offset, and sometimes
it is used to hold a pointer.  This patch changes it to a union containing
void * and dma_addr_t.  get/set accessors are also provided, because it was
getting a bit ugly to get to the actual data.

Signed-off-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/sysdev/dart_iommu.c b/arch/powerpc/sysdev/dart_iommu.c
index 89639ec..ae3c4db 100644
--- a/arch/powerpc/sysdev/dart_iommu.c
+++ b/arch/powerpc/sysdev/dart_iommu.c
@@ -297,7 +297,7 @@
 	/* We only have one iommu table on the mac for now, which makes
 	 * things simple. Setup all PCI devices to point to this table
 	 */
-	dev->dev.archdata.dma_data = &iommu_table_dart;
+	set_iommu_table_base(&dev->dev, &iommu_table_dart);
 }
 
 static void pci_dma_bus_setup_dart(struct pci_bus *bus)