eventdev: add new software timer adapter

This patch introduces a new version of the event timer adapter software
PMD. In the original design, timer event producer lcores in the primary
and secondary processes enqueued event timers into a ring, and a
service core in the primary process dequeued them and processed them
further.  To improve performance, this version does away with the ring
and lets lcores insert timers directly into timer skiplist data
structures; the service core directly accesses the lists as well, when
looking for timers that have expired.

To compare the burst and non-burst performance of the original and new
versions of the software event timer adapter, I ran the following
commands:

$ sudo ./build/app/dpdk-test-eventdev -c 0xFFE -s 0xC --vdev=event_sw0 \
-- --test=perf_queue --plcores=4,5,6 --wlcore=7,8,9 --stlist=p \
--prod_type_timerdev --worker_deq_depth=32

$ sudo ./build/app/dpdk-test-eventdev -c 0xFFE -s 0xC --vdev=event_sw0 \
-- --test=perf_queue --plcores=4,5,6 --wlcore=7,8,9 --stlist=p \
--prod_type_timerdev_burst --worker_deq_depth=32

With the new version, I see a 151% improvement in throughput for the
non-burst case, and a 270% improvement in throughput for the burst case.
I also see a 53% improvement in arm latency in the non-burst case and a
65% improvement in arm latency in the burst case.

Note: To perform the test,  I commented out a check in the original
version that checks the adapter tick interval against a minimum value.

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