ia64: Use accessor functions all over the place

Use the proper accessor functions instead of open coded irq_desc access.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/ia64/sn/kernel/irq.c b/arch/ia64/sn/kernel/irq.c
index 79ef3d0..b2aa793 100644
--- a/arch/ia64/sn/kernel/irq.c
+++ b/arch/ia64/sn/kernel/irq.c
@@ -273,15 +273,13 @@
 void sn_irq_init(void)
 {
 	int i;
-	struct irq_desc *base_desc = irq_desc;
 
 	ia64_first_device_vector = IA64_SN2_FIRST_DEVICE_VECTOR;
 	ia64_last_device_vector = IA64_SN2_LAST_DEVICE_VECTOR;
 
 	for (i = 0; i < NR_IRQS; i++) {
-		if (base_desc[i].chip == &no_irq_chip) {
-			base_desc[i].chip = &irq_type_sn;
-		}
+		if (irq_get_chip(i) == &no_irq_chip)
+			irq_set_chip(i, &irq_type_sn);
 	}
 }