net/virtio: fix check scatter on all Rx queues
net/virtio: fix check scatter on all Rx queues

This patch fixes the wrong way to obtain virtqueue.
The end of virtqueue cannot be judged based on whether
the array is NULL.

Fixes: 4e8169eb0d2d ("net/virtio: fix Rx scatter offload")
Cc: stable@dpdk.org

Signed-off-by: Zhihong Peng <162b9a56f203c5263114c834d81148c08960c77e@intel.com>
Reviewed-by: Maxime Coquelin <9a2667dee3b90866bbc9c2696cff2b7d5616c95a@redhat.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk