net/mlx5: fix initialization of steering registers

net/mlx5: fix initialization of steering registers

The mlx5_flow_action_copy_mreg structure contains a field called src
type enum modify_reg, similarly the mlx5_rte_flow_item_tag field
contains a field called id type enum modify_reg.
The enum modify_reg variable represents different registers in the
system and it also has a field called REG_NONE whose value is 0 which
means that the register does not exist.

The flow_mreg_add_copy_action function sets a variable of struct
mlx5_flow_action_copy_mreg type, and initializes the src field to be 0.
Similarly the flow_create_split_metadata function sets a variable of
struct mlx5_rte_flow_item_tag type and initializes the id field to be 0.
In both functions, they initialize a enum modify_reg type variable with
an int type value while modify_reg has an appropriate field for that
value (REG_NONE).

Replace assigning 0 with REG_NONE in both functions.

Fixes: dd3c774f6ffb ("net/mlx5: add metadata register copy table")
Fixes: 71e254bc0294 ("net/mlx5: split Rx flows to provide metadata copy")
Cc: stable@dpdk.org
Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>