KVM: convert slots_lock to a mutex

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index f326a6f..f01392f 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -372,9 +372,9 @@
 	kvm_ioapic_reset(ioapic);
 	kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
 	ioapic->kvm = kvm;
-	down_write(&kvm->slots_lock);
+	mutex_lock(&kvm->slots_lock);
 	ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, &ioapic->dev);
-	up_write(&kvm->slots_lock);
+	mutex_unlock(&kvm->slots_lock);
 	if (ret < 0)
 		kfree(ioapic);