net/mlx5: Fix MLX5_CMD_OP_MAX to be defined correctly

Having MLX5_CMD_OP_MAX on another file causes us to repeatedly miss
accounting new commands added to the driver and hence there're no entries
for them in debugfs. To solve that, we integrate it into the commands enum
as the last entry.

Fixes: 34a40e689393 ('net/mlx5_core: Introduce modify flow table command')
Signed-off-by: Shahar Klein <shahark@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>