net/mlx4_en: Change log level from error to debug for vlan related messages

The port vlan table size is 126 (used for IBoE) so after 126 we will
not have space and the user need to see it only in debug print and not
error.

Signed-off-by: Aviad Yehezkel <aviadye@mellanox.com>
Reviewed-by: Yevgeny Petrilin <yevgenyp@mellanox.com>
Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>