irqchip: Remove unused include

The "irqchip.h" include here is not needed as the only thing in
irqchip.h is IRQCHIP_DECLARE which this file doesn't use. Drop
it.
Reported-by: NJiri Kosina <jkosina@suse.cz>
Signed-off-by: NStephen Boyd <sboyd@codeaurora.org>
Link: http://lkml.kernel.org/r/531F7765.40207@codeaurora.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

drivers/irqchip/irqchip.c

@@ -12,8 +12,6 @@
 #include <linux/of_irq.h>
 #include <linux/irqchip.h>
 
-#include "irqchip.h"
-
 /*
  * This special of_device_id is the sentinel at the end of the
  * of_device_id[] array of all irqchips. It is automatically placed at