genirq: remove irq_to_desc_alloc

Remove the leftover of sparseirqs.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/kernel/irqinit_64.c b/arch/x86/kernel/irqinit_64.c
index d17fbc2..ff02353 100644
--- a/arch/x86/kernel/irqinit_64.c
+++ b/arch/x86/kernel/irqinit_64.c
@@ -144,7 +144,7 @@
 
 	for (i = 0; i < 16; i++) {
 		/* first time call this irq_desc */
-		struct irq_desc *desc = irq_to_desc_alloc(i);
+		struct irq_desc *desc = irq_to_desc(i);
 
 		desc->status = IRQ_DISABLED;
 		desc->action = NULL;