net/mlx5: fix zero value validation for metadata

net/mlx5: fix zero value validation for metadata

MARK and META items are interrelated with datapath -
they might move from/to the applications in mbuf.

zero value for these items has the special meaning -
it means "no metadata are provided", not zero values
are treated by applications and PMD as valid ones.

Moreover in the flow engine domain the value zero is
acceptable to match and set, and we should allow to
specify zero values as rte_flow parameters for the
META and MARK items and actions. In the same time
zero mask has no meaning and should be rejected
on validation stage.

Fixes: fcc8d2f716fd ("net/mlx5: extend flow metadata support")
Fixes: e554b672aa05 ("net/mlx5: support flow tag")
Fixes: 55deee1715f0 ("net/mlx5: extend flow mark support")
Cc: stable@dpdk.org
Signed-off-by: Wisam Jaddo <wisamm@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>