netdev-dpdk: Minor cleanup of netdev_dpdk_send__.

netdev-dpdk: Minor cleanup of netdev_dpdk_send__.

The variable 'cnt' is initialized and reused in multiple function calls
inside netdev_dpdk_send__() and is confusing sometimes. Instead introduce
'batch_cnt' to hold the original packet count and 'tx_cnt' to store
the final packet count resulting after filtering and qos operations.

Finally 'tx_cnt' packets gets transmitted on the respective 'qid'.

Signed-off-by: Bhanuprakash Bodireddy <bhanuprakash.bodireddy@intel.com>
Signed-off-by: Darrell Ball <dlu998@gmail.com>