examples/l3fwd: add framework for event device

examples/l3fwd: add framework for event device

Add framework to enable event device as a producer of packets.
To switch between event mode and poll mode the following options
have been added:
	`--mode="eventdev"` or `--mode="poll"`
Allow the user to select the schedule type to be either
RTE_SCHED_TYPE_ORDERED, RTE_SCHED_TYPE_ATOMIC or RTE_SCHED_TYPE_PARALLEL
through:
	`--eventq-sched="ordered"` or `--eventq-sched="atomic"` or
		`--eventq-sched="parallel"`
Allow the user to specify the number of Rx queues to be connected to
event queue using:
	`--event-eth-rxqs`

Poll mode is still the default operation mode.

Signed-off-by: Sunil Kumar Kori <skori@marvell.com>
Signed-off-by: Nipun Gupta <nipun.gupta@nxp.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>