More optimizations for Tx and Rx loops

More optimizations for Tx and Rx loops

  1) Parse multiple output packets in loop.
  2) Remove checking for error flags, they are never set because
     ODP parser is disabled.
  3) Do not call vlib_buffer_advance if not necessary.
  4) Remove lock in TX path. Queues are synchronized by ODP.
  5) Optimize detection of packet type.
  6) Create a wrapper for call to odp_packet_user_area.

Change-Id: Ib50c9be9a62d67824b58ef2cd443b7fc59471655
Signed-off-by: Michal Mazur <[email protected]>