This patch implements the ops rx_queue_count for vhost PMD by adding
a helper function rte_vhost_rx_queue_count in vhost lib.
The ops rx_queue_count gets vhost RX queue avail count and helps to
understand the queue fill level.
Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Acked-by: Ciara Loftus <ciara.loftus@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>