event/opdl: add OPDL ring infrastructure library

event/opdl: add OPDL ring infrastructure library

OPDL ring is the core infrastructure of OPDL PMD. OPDL ring library
provide the core data structure and core helper function set. The Ring
implements a single ring multi-port/stage pipelined packet distribution
mechanism. This mechanism has the following characteristics:

• No multiple queue cost, therefore, latency is significant reduced.
• Fixed dependencies between queue/ports is more suitable for complex.
  fixed pipelines of stateless packet processing (static pipeline).
• Has decentralized distribution (no scheduling core).
• Packets remain in order (no reorder core(s)).
* Update build system to enable compilation.

Signed-off-by: Liang Ma <liang.j.ma@intel.com>
Signed-off-by: Peter Mccarthy <peter.mccarthy@intel.com>
Reviewed-by: Seán Harte <seanbh@gmail.com>