of: Fix dereferencing node name in debug output to be safe

Several locations in the of_address and of_irq code dereference the
full_name parameter from a device_node pointer without checking if the
pointer is valid.  This patch switches to use of_node_full_name() which
always checks the pointer.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
diff --git a/drivers/of/address.c b/drivers/of/address.c
index b55c218..71180b9 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -489,7 +489,7 @@
 	int na, ns, pna, pns;
 	u64 result = OF_BAD_ADDR;
 
-	pr_debug("OF: ** translation for device %s **\n", dev->full_name);
+	pr_debug("OF: ** translation for device %s **\n", of_node_full_name(dev));
 
 	/* Increase refcount at current level */
 	of_node_get(dev);
@@ -504,13 +504,13 @@
 	bus->count_cells(dev, &na, &ns);
 	if (!OF_CHECK_COUNTS(na, ns)) {
 		printk(KERN_ERR "prom_parse: Bad cell count for %s\n",
-		       dev->full_name);
+		       of_node_full_name(dev));
 		goto bail;
 	}
 	memcpy(addr, in_addr, na * 4);
 
 	pr_debug("OF: bus is %s (na=%d, ns=%d) on %s\n",
-	    bus->name, na, ns, parent->full_name);
+	    bus->name, na, ns, of_node_full_name(parent));
 	of_dump_addr("OF: translating address:", addr, na);
 
 	/* Translate */