net/mlx5: fix unnecessary init in mark conversion

net/mlx5: fix unnecessary init in mark conversion

The flow_dv_convert_action_mark function defines an array of
field_modify_info structures and initializes the first entity.

In the first entity id field, it initializes to 0, even though its type
is an enum that has no value of 0.
In fact, the function does not use this id field before assigning the
appropriate register id into it, so the initialization is unnecessary.
Moreover, this initialization is int into enum, and it would be better
not to create a type conflict for no reason.

Wait for the first entity initialization until the appropriate register
id is already known.

Fixes: 55deee1715f0 ("net/mlx5: extend flow mark support")
Cc: stable@dpdk.org
Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>