net/mlx5e: Fix ETS BW check

Fix bug that allows ets bw sum to be 0% when ets tc type exists.

Fixes: 08fb1dac ('net/mlx5e: Support DCBNL IEEE ETS')
Signed-off-by: Moshe Shemesh <moshe@mellanox.com>
Reviewed-by: Huy Nguyen <huyn@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>