of: Make sure attached nodes don't carry along extra children

The child pointer does not get cleared when attaching new nodes which
could cause the tree to be inconsistent. Clear the child pointer in
__of_attach_node() to be absolutely sure that the structure remains in a
consistent layout.
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/dynamic.c

@@ -98,6 +98,7 @@ int of_property_notify(int action, struct device_node *np,
 
 void __of_attach_node(struct device_node *np)
 {
+	np->child = NULL;
 	np->sibling = np->parent->child;
 	np->allnext = np->parent->allnext;
 	np->parent->allnext = np;