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/kernel/pci-common.c b/arch/powerpc/kernel/pci-common.c
index e9f4840..bb8209e 100644
--- a/arch/powerpc/kernel/pci-common.c
+++ b/arch/powerpc/kernel/pci-common.c
@@ -1117,7 +1117,7 @@
 
 		/* Hook up default DMA ops */
 		sd->dma_ops = pci_dma_ops;
-		sd->dma_data = (void *)PCI_DRAM_OFFSET;
+		set_dma_offset(&dev->dev, PCI_DRAM_OFFSET);
 
 		/* Additional platform DMA/iommu setup */
 		if (ppc_md.pci_dma_dev_setup)