app/testpmd: add queue based priority flow control command

app/testpmd: add queue based priority flow control command

Patch adds command line options to configure queue based
priority flow control.

- Syntax command is given as below:

set pfc_queue_ctrl <port_id> rx <on|off> <tx_qid> <tx_tc> \
	tx <on|off> <rx_qid> <rx_tc> <pause_time>

- Example command to configure queue based priority flow control
  on rx and tx side for port 0, Rx queue 0, Tx queue 0 with pause
  time 2047

testpmd> set pfc_queue_ctrl 0 rx on 0 0 tx on 0 0 2047

Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>