powerpc: Use device_type helpers to access the node type

Remove directly accessing device_node.type pointer and use the
accessors instead. This will eventually allow removing the type
pointer.

Replace the open coded iterating over child nodes with
for_each_child_of_node() while we're here.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/isa-bridge.c

@@ -327,8 +327,7 @@ static int isa_bridge_notify(struct notifier_block *nb, unsigned long action,
 		/* Check if we have no ISA device, and this happens to be one,
 		 * register it as such if it has an OF device
 		 */
-		if (!isa_bridge_devnode && devnode && devnode->type &&
-		    !strcmp(devnode->type, "isa"))
+		if (!isa_bridge_devnode && of_node_is_type(devnode, "isa"))
 			isa_bridge_find_late(pdev, devnode);
 
 		return 0;