eventdev: introduce adapter flags for periodic mode

eventdev: introduce adapter flags for periodic mode

A timer adapter in periodic mode can be used to arm periodic timers.
This patch adds flags used to advertise capability and configure timer
adapter in periodic mode. Capability flag should be set for adapters
which support periodic mode.

Below is a programming sequence on the usage:
	/* check for periodic mode support by reading capability. */
	rte_event_timer_adapter_caps_get(...);

	/* create adapter in periodic mode by setting periodic flag
	   (RTE_EVENT_TIMER_ADAPTER_F_PERIODIC) and resolution. */
	rte_event_timer_adapter_create_ext(...);

	/* arm periodic timer of configured resolution */
	rte_event_timer_arm_burst(...);

	/* timer event will be periodically generated at configured
	   resolution till cancel is called. */
	while (running) { rte_event_dequeue_burst(...); }

	/* cancel periodic timer which stops generating events */
	rte_event_timer_cancel_burst(...);

Signed-off-by: Shijith Thotton <sthotton@marvell.com>
Acked-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>