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>