app/testpmd: support IPv4 fragments

app/testpmd: support IPv4 fragments

This patch updates testpmd CLI to support fragment_offset field of
IPv4 header item.

To match on non-fragmented IPv4 packets, need to use pattern:
... ipv4 fragment_offset spec 0 fragment_offset mask 0x3fff ...
To match on fragmented IPv4 packets, need to use pattern:
... ipv4 fragment_offset spec 1 fragment_offset last 0x3fff
fragment_offset mask 0x3fff ...
(Use the full available range 1 to 0x3fff to include all possible
values.)
To match on any IPv4 packets, fragmented and non-fragmented,
the fragment_offset field should not be specified for match.

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