net/mlx5e: Refine ets validation function

Removed an error message received when configuring ETS total
bandwidth to be zero.
Our hardware doesn't support such configuration, so we shall
reject it in the driver. Nevertheless, we removed the error message
in order to eliminate error messages caused by old userspace tools
who try to pass such configuration.

Fixes: ff089191 ("net/mlx5e: Fix ETS BW check")
Signed-off-by: Shay Agroskin <shayag@mellanox.com>
Reviewed-by: Huy Nguyen <huyn@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>