net/mlx5_core: Use the right inbox struct in destroy mkey command

struct mlx5_query_mkey_mbox_in rather than mlx5_destroy_mkey_mbox_in

Signed-off-by: Achiad Shochat <achiad@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>