net/mlx5e: Print a warning when LRO feature is dropped or not allowed

When user enables LRO via ethtool and if the RQ mode is legacy,
mlx5e_fix_features drops the request without any explanation.
Add netdev_warn to cover this case.

Fixes: 6c3a823e ("net/mlx5e: RX, Remove HW LRO support in legacy RQ")
Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>