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/io_apic.c b/arch/x86/kernel/io_apic.c
index 6836105..e03bc0f 100644
--- a/arch/x86/kernel/io_apic.c
+++ b/arch/x86/kernel/io_apic.c
@@ -1257,11 +1257,7 @@
 {
 	struct irq_desc *desc;
 
-	/* first time to use this irq_desc */
-	if (irq < 16)
-		desc = irq_to_desc(irq);
-	else
-		desc = irq_to_desc_alloc(irq);
+	desc = irq_to_desc(irq);
 
 	if ((trigger == IOAPIC_AUTO && IO_APIC_irq_trigger(irq)) ||
 	    trigger == IOAPIC_LEVEL)
diff --git a/arch/x86/kernel/irqinit_32.c b/arch/x86/kernel/irqinit_32.c
index 9092103..a8d3599 100644
--- a/arch/x86/kernel/irqinit_32.c
+++ b/arch/x86/kernel/irqinit_32.c
@@ -70,7 +70,7 @@
 	 */
 	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;
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;