net/mlx5e: Fix set vf link state error flow

Before this commit the ndo always returned success.
Fix that.

Fixes: 1ab2068a

 ("net/mlx5: Implement vports admin state backup/restore")
Signed-off-by: Roi Dayan <roid@mellanox.com>
Reviewed-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>