irqdomain: Replace open coded of_node_to_fwnode()

of_node_to_fwnode() should be used for conversion.  Replace the open coded
variant of it in of_phandle_args_to_fwspec().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20201030165919.86234-4-andriy.shevchenko@linux.intel.com

kernel/irq/irqdomain.c

@@ -737,7 +737,7 @@ static void of_phandle_args_to_fwspec(struct device_node *np, const u32 *args,
 {
 	int i;
 
-	fwspec->fwnode = np ? &np->fwnode : NULL;
+	fwspec->fwnode = of_node_to_fwnode(np);
 	fwspec->param_count = count;
 
 	for (i = 0; i < count; i++)