ARM: dt: create a DT header for the GIC

The ARM GIC binding defines a few custom cells and flags for its IRQ
specifier. Provide names for those.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NRob Herring <rob.herring@calxeda.com>

include/dt-bindings/interrupt-controller/arm-gic.h

+/*
+ * This header provides constants for the ARM GIC.
+ */
+
+#ifndef _DT_BINDINGS_INTERRUPT_CONTROLLER_ARM_GIC_H
+#define _DT_BINDINGS_INTERRUPT_CONTROLLER_ARM_GIC_H
+
+#include <dt-bindings/interrupt-controller/irq.h>
+
+/* interrupt specific cell 0 */
+
+#define GIC_SPI 0
+#define GIC_PPI 1
+
+/*
+ * Interrupt specifier cell 2.
+ * The flaggs in irq.h are valid, plus those below.
+ */
+#define GIC_CPU_MASK_RAW(x) ((x) << 8)
+#define GIC_CPU_MASK_SIMPLE(num) GIC_CPU_MASK_RAW((1 << (num)) - 1)
+
+#endif