Field IDs for the MODIFY_FIELD action lack doxygen comments
and not visible in online DPDK documentation because of that.
Provide a meaningful description for every Field ID for the
rte_flow_field_id enumeration.
Fixes: 73b68f4c54a0 ("ethdev: introduce generic modify flow action")
Cc: stable@dpdk.org
Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>