table: add dedicated params struct for cuckoo hash

table: add dedicated params struct for cuckoo hash

Add dedicated parameter structure for cuckoo hash. The cuckoo hash from
librte_hash uses slightly different prototype for the hash function (no
key_mask parameter, 32-bit seed and return value) that require either
of the following approaches:
   1/ Function pointer conversion: gcc 8.1 warning [1], misleading [2]
   2/ Union within the parameter structure: pollutes a very generic API
      parameter structure with some implementation dependent detail
      (i.e. key mask not available for one of the available
      implementations)
   3/ Using opaque pointer for hash function: same issue from 2/
   4/ Different parameter structure: avoid issue from 2/; hopefully,
      it won't be long before librte_hash implements the key mask feature,
      so the generic API structure could be used.

[1] http://www.dpdk.org/ml/archives/dev/2018-April/094950.html
[2] http://www.dpdk.org/ml/archives/dev/2018-April/096250.html

Fixes: 5a80bf0ae613 ("table: add cuckoo hash")
Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>