efd: new Elastic Flow Distributor library

efd: new Elastic Flow Distributor library

Elastic Flow Distributor (EFD) is a distributor library that uses
perfect hashing to determine a target/value for a given incoming flow key.
It has the following advantages:

- First, because it uses perfect hashing, it does not store
  the key itself and hence lookup performance is not dependent
  on the key size.

- Second, the target/value can be any arbitrary value hence
  the system designer and/or operator can better optimize service rates
  and inter-cluster network traffic locating.

- Third, since the storage requirement is much smaller than a hash-based
  flow table (i.e. better fit for CPU cache), EFD can scale to
  millions of flow keys.
  Finally, with current optimized library implementation performance
  is fully scalable with number of CPU cores.

Signed-off-by: Byron Marohn <byron.marohn@intel.com>
Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
Signed-off-by: Saikrishna Edupuganti <saikrishna.edupuganti@intel.com>
Acked-by: Christian Maciocco <christian.maciocco@intel.com>