iavf: Support IPv6 Flow Director filters

Support the addition and deletion of IPv6 filters.

Supported fields are: src-ip, dst-ip, src-port, dst-port and l4proto
Supported flow-types are: tcp6, udp6, sctp6, ip6, ah6, esp6

Example usage:
ethtool -N ens787f0v0 flow-type tcp6 src-ip 2001::2 \
  dst-ip CDCD:910A:2222:5498:8475:1111:3900:2020 \
  tclass 1 src-port 22 dst-port 23 action 7

L2TPv3 over IP with 'Session ID' 17:
ethtool -N ens787f0v0 flow-type ip6 l4proto 115 l4data 17 action 7

Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
Tested-by: Chen Bo <BoX.C.Chen@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>