irqchip: vic: add include of linux/irq.h

With the include of <asm/mach/irq.h> removed, the implicit include of
linux/irq.h also disappeared. Add it back.
Signed-off-by: Olof Johansson <olof@lixom.net>

drivers/irqchip/irq-vic.c

@@ -23,6 +23,7 @@
 #include <linux/init.h>
 #include <linux/list.h>
 #include <linux/io.h>
+#include <linux/irq.h>
 #include <linux/irqdomain.h>
 #include <linux/of.h>
 #include <linux/of_address.h>