of/irq: Rework of_irq_count()

The of_irq_to_resource() helper that is used to implement of_irq_count()
tries to resolve interrupts and in fact creates a mapping for resolved
interrupts. That's pretty heavy lifting for something that claims to
just return the number of interrupts requested by a given device node.

Instead, use the more lightweight of_irq_map_one(), which, despite the
name, doesn't create an actual mapping. Perhaps a better name would be
of_irq_translate_one().
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Rob Herring <rob.herring@calxeda.com>
[grant.likely: fixup s/of_irq_map_one/of_irq_parse_one/]
Signed-off-by: Grant Likely <grant.likely@linaro.org>

drivers/of/irq.c

@@ -373,9 +373,10 @@ EXPORT_SYMBOL_GPL(of_irq_to_resource);
  */
 int of_irq_count(struct device_node *dev)
 {
+	struct of_phandle_args irq;
 	int nr = 0;
 
-	while (of_irq_to_resource(dev, nr, NULL))
+	while (of_irq_parse_one(dev, nr, &irq) == 0)
 		nr++;
 
 	return nr;