eventdev: add errno-style return values

eventdev: add errno-style return values

This commit adds rte_errno return values to rte_event_enqueue_burst() and
rte_event_dequeue_burst().

These return values allows user software to differentiate between an
invalid argument (such as an invalid queue_id or sched_type in an enqueued
event) and backpressure from the event device.

The port and device ID checks are placed in RTE_LIBRTE_EVENTDEV_DEBUG
header guards to avoid the performance hit in non-debug execution.

Signed-off-by: Gage Eads <gage.eads@intel.com>