arch/powerpc: Move dma_mask from of_device into pdev_archdata

By moving dma_mask into pdev_archdata, and adding archdata to
struct of_device, it makes it possible to substitute of_device
with struct platform_device, which is a stepping stone to
removing the of_platform bus entirely.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/macintosh/macio_asic.c b/drivers/macintosh/macio_asic.c
index 67fe13f..48a5f04 100644
--- a/drivers/macintosh/macio_asic.c
+++ b/drivers/macintosh/macio_asic.c
@@ -374,8 +374,8 @@
 	dev->bus = &chip->lbus;
 	dev->media_bay = in_bay;
 	dev->ofdev.dev.of_node = np;
-	dev->ofdev.dma_mask = 0xffffffffUL;
-	dev->ofdev.dev.dma_mask = &dev->ofdev.dma_mask;
+	dev->ofdev.archdata.dma_mask = 0xffffffffUL;
+	dev->ofdev.dev.dma_mask = &dev->ofdev.archdata.dma_mask;
 	dev->ofdev.dev.parent = parent;
 	dev->ofdev.dev.bus = &macio_bus_type;
 	dev->ofdev.dev.release = macio_release_dev;