of: Export of_irq_find_parent()

We have platform code that needs to find a node's interrupt parent, so
export of_irq_find_parent() so we can use it.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/drivers/of/irq.c b/drivers/of/irq.c
index 75b0d3c..9f689f1d 100644
--- a/drivers/of/irq.c
+++ b/drivers/of/irq.c
@@ -56,7 +56,7 @@
  * Returns a pointer to the interrupt parent node, or NULL if the interrupt
  * parent could not be determined.
  */
-static struct device_node *of_irq_find_parent(struct device_node *child)
+struct device_node *of_irq_find_parent(struct device_node *child)
 {
 	struct device_node *p;
 	const __be32 *parp;