ARM: dt: add header to define IRQ flags

Many IRQ device tree bindings use the same flags. Create a header to
define those.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NRob Herring <rob.herring@calxeda.com>

include/dt-bindings/interrupt-controller/irq.h

+/*
+ * This header provides constants for most IRQ bindings.
+ *
+ * Most IRQ bindings include a flags cell as part of the IRQ specifier.
+ * In most cases, the format of the flags cell uses the standard values
+ * defined in this header.
+ */
+
+#ifndef _DT_BINDINGS_INTERRUPT_CONTROLLER_IRQ_H
+#define _DT_BINDINGS_INTERRUPT_CONTROLLER_IRQ_H
+
+#define IRQ_TYPE_NONE		0
+#define IRQ_TYPE_EDGE_RISING	1
+#define IRQ_TYPE_EDGE_FALLING	2
+#define IRQ_TYPE_EDGE_BOTH	(IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_EDGE_RISING)
+#define IRQ_TYPE_LEVEL_HIGH	4
+#define IRQ_TYPE_LEVEL_LOW	8
+
+#endif