app/eventdev: remove redundant enqueue in burst Tx

app/eventdev: remove redundant enqueue in burst Tx

For eventdev pipeline test, in burst_tx cases, there is no needed to
set ev.op as RTE_EVENT_OP_RELEASE and call pipeline_event_enqueue_burst
to release events. This is because for tx mode(internal_port=true),
the capability "implicit_release" of dev is enabled, and the app can
release events by "rte_event_dequeue_burst" rather than enqueue.

Fixes: 314bcf58ca8f ("app/eventdev: add pipeline queue worker functions")
Cc: stable@dpdk.org
Signed-off-by: Feifei Wang <feifei.wang2@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>