genirq: Reuse existing can set affinty check

Add a !desc check while at it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 84a0a9c..550ae97 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -73,8 +73,8 @@
 {
 	struct irq_desc *desc = irq_to_desc(irq);
 
-	if (!irqd_can_balance(&desc->irq_data) || !desc->irq_data.chip ||
-	    !desc->irq_data.chip->irq_set_affinity)
+	if (!desc || !irqd_can_balance(&desc->irq_data) ||
+	    !desc->irq_data.chip || !desc->irq_data.chip->irq_set_affinity)
 		return 0;
 
 	return 1;