irqchip: exynos-combiner: Fix compilation error on ARM64

The following compilation error occurs on 64-bit Exynos7 SoC:

drivers/irqchip/exynos-combiner.c: In function ‘combiner_irq_domain_map’:
drivers/irqchip/exynos-combiner.c:162:2: error: implicit declaration of function ‘set_irq_flags’ [-Werror=implicit-function-declaration]
  set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
  ^
drivers/irqchip/exynos-combiner.c:162:21: error: ‘IRQF_VALID’ undeclared (first use in this function)
  set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);
                     ^
drivers/irqchip/exynos-combiner.c:162:21: note: each undeclared identifier is reported only once for each function it appears in
drivers/irqchip/exynos-combiner.c:162:34: error: ‘IRQF_PROBE’ undeclared (first use in this function)
  set_irq_flags(irq, IRQF_VALID | IRQF_PROBE);

Fix the build error by including linux/interrupt.h.
Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lkml.kernel.org/r/1409722329-18309-1-git-send-email-ch.naveen@samsung.comSigned-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/exynos-combiner.c

@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/irqdomain.h>
 #include <linux/irqchip/chained_irq.h>
+#include <linux/interrupt.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>