net/mlx5: Disallow RoCE on multi port slave device

In dual port mode, setting roce enabled/disable for the slave device
have no effect. e.g.: the slave device roce status remain unchanged.
Therefore disable it and add an error message.
Enable or disable roce of the master device affect both master and slave
devices.

Fixes: cc9defcb ("net/mlx5: Handle "enable_roce" devlink param")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>