net/mlx4_core: Return the error value in case of command initialization failure

If mlx4_cmd_init() failed, the init_one function returned
success, although no resources were opened.

Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>