[PATCH] ia64: use has_8259 in acpi_register_irq()

acpi_madt is marked as __initdata, so an attempt to use
acpi_register_irq() after we discarded init sections would cause us to
dereference a random location.  Everywhere else uses has_8259 anyway.

arch/ia64/kernel/acpi.c

@@ -720,7 +720,7 @@ acpi_register_irq (u32 gsi, u32 polarity, u32 trigger)
 {
 	int vector = 0;
 
-	if (acpi_madt->flags.pcat_compat && (gsi < 16))
+	if (has_8259 && (gsi < 16))
 		return isa_irq_to_vector(gsi);
 
 	if (!iosapic_register_intr)