net/mlx5: fix Tx metadata endianness in data path

net/mlx5: fix Tx metadata endianness in data path

The metadata can be set in the mbuf dynamic field and then used in
flow rules steering for egress direction. The hardware requires
network order for both the insertion of a rule and sending a packet.
Indeed, there is no strict restriction for the endianness. The order
for sending a packet and its steering rule should be consistent.

In the past, there was no endianness conversion due to the
performance reason. The flow rule converted the metadata into little
endian for hardware (if needed) and the packet hit the flow rule also
with little endian.

After the metadata was converted to big endian, the missing adaption
in the data path resulted in a flow miss of the egress packets.

Converting the metadata to big endian before posting a WQE to the
hardware solves this issue.

Fixes: b57e414b48c0 ("net/mlx5: convert meta register to big-endian")
Cc: stable@dpdk.org
Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>