Add support for creating filters for GTP-U and GTP-C in switchdev mode. Add
support for parsing GTP-specific options (QFI and PDU type) and TEID.

By default, a filter for GTP-U will be added. To add a filter for GTP-C,
specify enc_dst_port = 2123, e.g.:

tc filter add dev $GTP0 ingress prio 1 flower enc_key_id 1337 \
enc_dst_port 2123 action mirred egress redirect dev $VF1_PR

Note: GTP-U with outer IPv6 offload is not supported yet.
Note: GTP-U with no payload offload is not supported yet.
Signed-off-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>