virtio_console: don't tie bufs to a vq

virtio_console: don't tie bufs to a vq

BugLink: http://bugs.launchpad.net/bugs/1778265
commit 2855b33514d290c51d52d94e25d3ef942cd4d578 upstream.

an allocated buffer doesn't need to be tied to a vq -
only vq->vdev is ever used. Pass the function the
just what it needs - the vdev.

Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>