virtio-9p-device: fix memleak in virtio_9p_device_unrealize

virtio-9p-device: fix memleak in virtio_9p_device_unrealize

v->vq forgot to cleanup in virtio_9p_device_unrealize, the memory leak
stack is as follow:

Direct leak of 14336 byte(s) in 2 object(s) allocated from:
  #0 0x7f819ae43970 (/lib64/libasan.so.5+0xef970)  ??:?
  #1 0x7f819872f49d (/lib64/libglib-2.0.so.0+0x5249d)  ??:?
  #2 0x55a3a58da624 (./x86_64-softmmu/qemu-system-x86_64+0x2c14624)  /mnt/sdb/qemu/hw/virtio/virtio.c:2327
  #3 0x55a3a571bac7 (./x86_64-softmmu/qemu-system-x86_64+0x2a55ac7)  /mnt/sdb/qemu/hw/9pfs/virtio-9p-device.c:209
  #4 0x55a3a58e7bc6 (./x86_64-softmmu/qemu-system-x86_64+0x2c21bc6)  /mnt/sdb/qemu/hw/virtio/virtio.c:3504
  #5 0x55a3a5ebfb37 (./x86_64-softmmu/qemu-system-x86_64+0x31f9b37)  /mnt/sdb/qemu/hw/core/qdev.c:876

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Pan Nengyuan <pannengyuan@huawei.com>
Message-Id: <20200117060927.51996-2-pannengyuan@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Acked-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit 9580d60e66d1543a0d79265c0085ee09b8782987)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>