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>

arch/powerpc/platforms/iseries/iommu.c

@@ -193,7 +193,7 @@ static void pci_dma_dev_setup_iseries(struct pci_dev *pdev)
 		pdn->iommu_table = iommu_init_table(tbl, -1);
 	else
 		kfree(tbl);
-	pdev->dev.archdata.dma_data = pdn->iommu_table;
+	set_iommu_table_base(&pdev->dev, pdn->iommu_table);
 }
 #else
 #define pci_dma_dev_setup_iseries	NULL