IPv6 DSCP field ID is missing from the original list of Field IDs
for MODIFY_FIELD action. Add it to support IPv6 header fully.
Add ipv6_dscp option for the corresponding header field in testpmd.
Fixes: 73b68f4c54a0 ("ethdev: introduce generic modify flow action")
Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
Acked-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>