irqdomain: Add forward declaration of fwnode_handle

irqdomain.h is a user of struct fwnode_handle. Add forward declaration of it.
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/20201030165919.86234-3-andriy.shevchenko@linux.intel.com

include/linux/irqdomain.h

@@ -37,6 +37,7 @@
 #include <linux/radix-tree.h>
 
 struct device_node;
+struct fwnode_handle;
 struct irq_domain;
 struct irq_chip;
 struct irq_data;