app/testpmd: support IPv6 fragments

app/testpmd: support IPv6 fragments

rte_flow update, following RFC [1], introduced has_frag_ext field for
IPv6 header item, used to indicate match on fragmented/non-fragmented
packets.
This patch updates testpmd CLI to support the new field.

To match on non-fragmented IPv6 packets, need to use pattern:
... ipv6 has_frag_ext spec 0 has_frag_ext mask 1 ...
To match on fragmented IPv6 packets, need to use pattern:
... ipv6 has_frag_ext spec 1 has_frag_ext mask 1 ...
To match on any IPv6 packets, the has_frag_ext field should
not be specified for match.

[1] https://mails.dpdk.org/archives/dev/2020-August/177257.html

Signed-off-by: Dekel Peled <dekelp@nvidia.com>
Acked-by: Ori Kam <orika@nvidia.com>