genirq: remove irq_to_desc_alloc

Remove the leftover of sparseirqs.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 570d1ea..e6f73db 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -28,7 +28,7 @@
 	unsigned long flags;
 
 	/* first time to use this irq_desc */
-	desc = irq_to_desc_alloc(irq);
+	desc = irq_to_desc(irq);
 	if (!desc) {
 		WARN(1, KERN_ERR "Trying to initialize invalid IRQ%d\n", irq);
 		return;