app/testpmd: support metadata as flow rule item

app/testpmd: support metadata as flow rule item

As described in [1], this series adds option to set metadata value
as match pattern when creating a new flow rule.

This patch introduces additional options in testpmd commands:
- New item type "meta" "data"
- New per-port offload flag "match_metadata".

It also adds commands to configure the tx_metadata value to use:
- New 'config' command takes a 32 bit value and stores it per port:
	port config <port_id> tx_metadata <value>
  testpmd will add to any Tx packet sent from this port the metadata
  value, and set ol_flags accordingly.
- A matching 'show' command is added to read the configured value:
	port config <port_id> tx_metadata <value>

[1] "ethdev: support metadata as flow rule criteria"

Signed-off-by: Dekel Peled <dekelp@mellanox.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>