net/virtio: move control queue configuration

net/virtio: move control queue configuration

Move the configuration of control queue in the configure callback.
This is needed by next commit, which introduces the reinitialization
of the device in the configure callback to change the feature flags.
Therefore, the control queue will have to be restarted at the same
place.

As virtio_dev_cq_queue_setup() is called from a place where
config->max_virtqueue_pairs is not available, we need to store this in
the private structure. It replaces max_rx_queues and max_tx_queues which
have the same value. The log showing the value of max_rx_queues and
max_tx_queues is also removed since config->max_virtqueue_pairs is
already displayed above.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>