bond: add mode 4

bond: add mode 4

This patch set add support for dynamic link aggregation (mode 4) to the
librte_pmd_bond library. This mode provides auto negotiation/configuration
of peers and well as link status changes monitoring using out of band
LACP (link aggregation control protocol) messages. For further details of
LACP specification see the IEEE 802.3ad/802.1AX standards. It is also
described here
https://www.kernel.org/doc/Documentation/networking/bonding.txt.

In this implementation we have an array of mode 4 settings for each slave.
There is also assumption that for every port is one aggregator (it might
be unused if better is found).

Difference in this implementation vs Linux implementation:
- this implementation it is not directly based on state machines but current
  state is calculated from actor and partner states (and other things too).

Some implementation details:
- during rx burst every packet Is checked if this is LACP or marker packet.
  If it is LACP frame it is passed to mode 4 logic using slaves rx ring  and
  removed from rx buffer before it is returned
- in tx burst, packets from mode 4 (if any) are injected into each slave.
- there is a timer running in background to process/produce mode 4
  frames form rx/to tx functions.

Some requirements for this mode:
- for LACP mode to work rx and tx burst functions must be invoked
  at least in 100ms intervals
- provided buffer to rx burst should be at least 2x slave count size. This is
  not needed but might increase performance especially during initial
  handshake.

Signed-off-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Acked-by: Declan Doherty <declan.doherty@intel.com>