x86: ioapic: Use new setup function in pre_init_apic_IRQ0()

Remove the duplicated code and call the function. It does not matter
whether we allocated the cfg before calling setup_local_APIC() and we
can set the irq chip and handler after that as well.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/apic/io_apic.c

@@ -4103,20 +4103,15 @@ void __init mp_register_ioapic(int id, u32 address, u32 gsi_base)
 /* Enable IOAPIC early just for system timer */
 void __init pre_init_apic_IRQ0(void)
 {
-	struct irq_cfg *cfg;
+	struct io_apic_irq_attr attr = { 0, 0, 0, 0 };
 
 	printk(KERN_INFO "Early APIC setup for system timer0\n");
 #ifndef CONFIG_SMP
 	physid_set_mask_of_physid(boot_cpu_physical_apicid,
 					 &phys_cpu_present_map);
 #endif
-	/* Make sure the irq descriptor is set up */
-	cfg = alloc_irq_and_cfg_at(0, 0);
-
 	setup_local_APIC();
 
-	add_pin_to_irq_node(cfg, 0, 0, 0);
+	io_apic_setup_irq_pin(0, 0, &attr);
 	set_irq_chip_and_handler_name(0, &ioapic_chip, handle_edge_irq, "edge");
-
-	setup_ioapic_irq(0, 0, 0, cfg, 0, 0);
 }