KVM: Take missing slots_lock for kvm_io_bus_unregister_dev()

In KVM_CREATE_IRQCHIP, kvm_io_bus_unregister_dev() is called without taking
slots_lock in the error handling path.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 48a48bd..70d224d 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -951,7 +951,9 @@
 			goto out;
 		r = kvm_setup_default_irq_routing(kvm);
 		if (r) {
+			mutex_lock(&kvm->slots_lock);
 			kvm_ioapic_destroy(kvm);
+			mutex_unlock(&kvm->slots_lock);
 			goto out;
 		}
 		break;