net/mlx5: Don't store reserved part in FTEs and FGs

The current code stores fte_match_param in the software representation
of FTEs and FGs. fte_match_param contains a large reserved area at the
bottom of the struct. Since downstream patches are going to hash this
part, we would like to avoid doing so on a reserved part.

Signed-off-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>