genirq: Add single IRQ reservation helper

For cases that wish to reserve a single IRQ at a given place simply
provide a wrapper in to the ranged reservation routine.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
LKML-Reference: <20101026071912.GD4733@linux-sh.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/irq.h

@@ -412,6 +412,11 @@ static inline void irq_free_desc(unsigned int irq)
 	irq_free_descs(irq, 1);
 }
 
+static inline int irq_reserve_irq(unsigned int irq)
+{
+	return irq_reserve_irqs(irq, 1);
+}
+
 #endif /* CONFIG_GENERIC_HARDIRQS */
 
 #endif /* !CONFIG_S390 */