common/mlx5: add flex parser DevX structures

common/mlx5: add flex parser DevX structures

The structures and other definitions will be used for the dynamic
flex parser creation via Devx command interface. These structures
will be used as some some intermediate variables and input
parameters for the parser creation API.
It is better to keep all members consistent with the PRM definition
even though some of them will not be used.

Signed-off-by: Bing Zhao <bingz@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>