[ARM] 3728/1: Restore missing CPU Hotplug irq helper

Patch from Thomas Gleixner

From: Thomas Gleixner <tglx@linutronix.de>

The genirq conversion of ARM lost a CPU Hotplug helper function.
Restore it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/irq.c

@@ -167,6 +167,16 @@ void __init init_IRQ(void)
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
+
+static void route_irq(struct irqdesc *desc, unsigned int irq, unsigned int cpu)
+{
+	pr_debug("IRQ%u: moving from cpu%u to cpu%u\n", irq, desc->cpu, cpu);
+
+	spin_lock_irq(&desc->lock);
+	desc->chip->set_affinity(irq, cpumask_of_cpu(cpu));
+	spin_unlock_irq(&desc->lock);
+}
+
 /*
  * The CPU has been marked offline.  Migrate IRQs off this CPU.  If
  * the affinity settings do not allow other CPUs, force them onto any