drivers/of: Export of_detach_node()

This exports of_detach_node() for PowerPC PowerNV PCI hotplug
driver. No functional changes introduced.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Rob Herring <robh@kernel.org>

drivers/of/dynamic.c

@@ -311,6 +311,7 @@ int of_detach_node(struct device_node *np)
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(of_detach_node);
 
 /**
  * of_node_release() - release a dynamically allocated node