irqdomain: Remove unused of_device_id forward declaration

There is no users of of_device_id in irqdomain.h. Drop 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/20201030165919.86234-2-andriy.shevchenko@linux.intel.com

include/linux/irqdomain.h

@@ -38,7 +38,6 @@
 
 struct device_node;
 struct irq_domain;
-struct of_device_id;
 struct irq_chip;
 struct irq_data;
 struct cpumask;