genirq: Convert irq_desc.lock to raw_spinlock

Convert locks which cannot be sleeping locks in preempt-rt to
raw_spinlocks.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/irq.h b/include/linux/irq.h
index a287cfc..451481c 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -192,7 +192,7 @@
 	unsigned int		irq_count;	/* For detecting broken IRQs */
 	unsigned long		last_unhandled;	/* Aging timer for unhandled count */
 	unsigned int		irqs_unhandled;
-	spinlock_t		lock;
+	raw_spinlock_t		lock;
 #ifdef CONFIG_SMP
 	cpumask_var_t		affinity;
 	unsigned int		node;