[PATCH] genirq: sem2mutex probe_sem -> probing_active

Convert the irq auto-probing semaphore to a mutex.  (This allows us to find
probing API usage bugs sooner, via the mutex debugging code.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>