net/mlx4_core: Fix return codes of unsupported operations

Functions __set_port_type and mlx4_check_port_params returned
-EINVAL while the proper return code is -EOPNOTSUPP as a
result of an unsupported operation. All drivers should generate
this and all users should check for it when detecting an
unsupported functionality.

Signed-off-by: Erez Alfasi <ereza@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>