x86/IO-APIC: adjust an otherwise pretty useless message

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/io_apic.c
+++ b/xen/arch/x86/io_apic.c
@@ -2164,8 +2164,8 @@ int io_apic_set_pci_routing (int ioapic,
     int vector;
 
     if (!IO_APIC_IRQ(irq)) {
-        printk(KERN_ERR "IOAPIC[%d]: Invalid reference to IRQ 0\n",
-               ioapic);
+        printk(KERN_ERR "IOAPIC[%d]: Invalid reference to IRQ %d\n",
+               ioapic, irq);
         return -EINVAL;
     }