kvm-stub: fix compilation

Non-KVM targets fail compilation on the uq/master branch.
Fix the prototype of kvm_irqchip_add_irqfd_notifier to match
the one in kvm-all.c.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>

kvm-stub.c

@@ -135,7 +135,8 @@ int kvm_irqchip_update_msi_route(KVMState *s, int virq, MSIMessage msg)
     return -ENOSYS;
 }
 
-int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n, int virq)
+int kvm_irqchip_add_irqfd_notifier(KVMState *s, EventNotifier *n,
+                                   EventNotifier *rn, int virq)
 {
     return -ENOSYS;
 }