genirq: Introduce IRQF_NODELAY to disable forced threading for an irq

Add the IRQF_NODELAY flag and implicitely mark all timer interrupts
IRQF_NODELAY by redefining IRQF_TIMER.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/interrupt.h

@@ -50,15 +50,19 @@
  * IRQF_IRQPOLL - Interrupt is used for polling (only the interrupt that is
  *                registered first in an shared interrupt is considered for
  *                performance reasons)
+ * IRQF_NODELAY - Interrupt is not force threaded
  */
 #define IRQF_DISABLED		0x00000020
 #define IRQF_SAMPLE_RANDOM	0x00000040
 #define IRQF_SHARED		0x00000080
 #define IRQF_PROBE_SHARED	0x00000100
-#define IRQF_TIMER		0x00000200
+#define __IRQF_TIMER		0x00000200
 #define IRQF_PERCPU		0x00000400
 #define IRQF_NOBALANCING	0x00000800
 #define IRQF_IRQPOLL		0x00001000
+#define IRQF_NODELAY		0x00002000
+
+#define IRQF_TIMER		(__IRQF_TIMER | IRQF_NODELAY)
 
 /*
  * Bits used by threaded handlers: