[PATCH] genirq: add IRQ_TYPE_SENSE_MASK

Add a #define for the mask of the part of IRQ_TYPE that represents the
trigger type.  I use that in my in-progress work as I've standardized the
way the irq description in the firmware device-tree get translated to linux
useable things by using those constants.  Having this mask to isolate the
"trigger type" part of the flags is useful in a few places.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>