powerpc/cell/iommu: Improve error message for missing node

Some devices don't have a correct node ID and thus can't be
attached to an iommu.

The message displayed by the iommu code isn't very useful if
you don't have a device-tree node as it tries to print the
device-tree path but not the struct device name.

Improve this by printing the device name as well.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/cell/iommu.c

@@ -550,7 +550,7 @@ static struct iommu_table *cell_get_iommu_table(struct device *dev)
 	 */
 	iommu = cell_iommu_for_node(dev_to_node(dev));
 	if (iommu == NULL || list_empty(&iommu->windows)) {
-		printk(KERN_ERR "iommu: missing iommu for %s (node %d)\n",
+		dev_err(dev, "iommu: missing iommu for %s (node %d)\n",
 		       of_node_full_name(dev->of_node), dev_to_node(dev));
 		return NULL;
 	}