iavf: Support for modifying SCTP RSS flow hashing

Provide the ability to enable SCTP RSS hashing by ethtool.

It gives users option of generating RSS hash based on the SCTP source
and destination ports numbers, IPv4 or IPv6 source and destination
addresses.

Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>