virtio-serial-bus: fix memory leak while attach virtio-serial-bus

ivqs/ovqs/c_ivq/c_ovq is forgot to cleanup in
virtio_serial_device_unrealize, the memory leak stack is as bellow:

Direct leak of 1290240 byte(s) in 180 object(s) allocated from:
    #0 0x7fc9bfc27560 in calloc (/usr/lib64/libasan.so.3+0xc7560)
    #1 0x7fc9bed6f015 in g_malloc0 (/usr/lib64/libglib-2.0.so.0+0x50015)
    #2 0x5650e02b83e7 in virtio_add_queue hw/virtio/virtio.c:2327
    #3 0x5650e02847b5 in virtio_serial_device_realize hw/char/virtio-serial-bus.c:1089
    qemu#4 0x5650e02b56a7 in virtio_device_realize hw/virtio/virtio.c:3504
    qemu#5 0x5650e03bf031 in device_set_realized hw/core/qdev.c:876
    qemu#6 0x5650e0531efd in property_set_bool qom/object.c:2080
    qemu#7 0x5650e053650e in object_property_set_qobject qom/qom-qobject.c:26
    qemu#8 0x5650e0533e14 in object_property_set_bool qom/object.c:1338
    qemu#9 0x5650e04c0e37 in virtio_pci_realize hw/virtio/virtio-pci.c:1801

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Cc: Laurent Vivier <lvivier@redhat.com>
Cc: Amit Shah <amit@kernel.org>
Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <1575444716-17632-3-git-send-email-pannengyuan@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>

hw/char/virtio-serial-bus.c

@@ -1126,9 +1126,17 @@ static void virtio_serial_device_unrealize(DeviceState *dev, Error **errp)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VirtIOSerial *vser = VIRTIO_SERIAL(dev);
+    int i;
 
     QLIST_REMOVE(vser, next);
 
+    virtio_delete_queue(vser->c_ivq);
+    virtio_delete_queue(vser->c_ovq);
+    for (i = 0; i < vser->bus.max_nr_ports; i++) {
+        virtio_delete_queue(vser->ivqs[i]);
+        virtio_delete_queue(vser->ovqs[i]);
+    }
+
     g_free(vser->ivqs);
     g_free(vser->ovqs);
     g_free(vser->ports_map);