of/irq: of_irq_init: add check for parent equal to child node

With the revert of "of/irq: of_irq_find_parent: check for parent equal to
child" (dc937280), we need another way to handle parent node equal
to the child node. This can simply be handled in of_irq_init by checking
for this condition.
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Tested-by: Pawel Moll <pawel.moll@arm.com>
Tested-by: Stephen Warren <swarren@nvidia.com>

drivers/of/irq.c

@@ -424,6 +424,8 @@ void __init of_irq_init(const struct of_device_id *matches)
 
 		desc->dev = np;
 		desc->interrupt_parent = of_irq_find_parent(np);
+		if (desc->interrupt_parent == np)
+			desc->interrupt_parent = NULL;
 		list_add_tail(&desc->list, &intc_desc_list);
 	}