[POWERPC] Generalise device_node flag interface

The struct device_node currently has a _flags variable, although
it's only used for one flag - OF_DYNAMIC.  Generalise the flag
accessors so we can use them with other flags in future.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom.c

@@ -1375,7 +1375,7 @@ static void of_node_release(struct kref *kref)
 	struct device_node *node = kref_to_device_node(kref);
 	struct property *prop = node->properties;
 
-	if (!OF_IS_DYNAMIC(node))
+	if (!of_node_check_flag(node, OF_DYNAMIC))
 		return;
 	while (prop) {
 		struct property *next = prop->next;