net/mlx5: Lag, Fix for loop when checking lag

The cited commit adds a for loop to check if each port supports lag
or not. But dev is not initialized correctly. Fix it by initializing
dev for each iteration.

Fixes: e87c6a83

 ("net/mlx5: E-switch, Fix duplicate lag creation")
Signed-off-by: Chris Mi <cmi@nvidia.com>
Reported-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20221129093006.378840-2-saeed@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>