net/virtio: fix queue flushing with vector Rx enabled

net/virtio: fix queue flushing with vector Rx enabled

When using vector Rx mode (use_simple_rx = 1), vq->vq_descx[] is not
kept up to date. To properly detach the mbufs in this case, browse
sw_ring[] instead, as it's done in virtqueue_rxvq_flush().

Since we need virtio_get_queue_type(), also move this function in
virtqueue.h as a static inline.

Fixes: fc3d66212fed ("virtio: add vector Rx")
Cc: stable@dpdk.org
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Yuanhan Liu <yliu@fridaylinux.org>