net/mlx5e: Add error print in ETS init

ETS initialization might fail, add a print to indicate
such failures.

Fixes: 08fb1dac ("net/mlx5e: Support DCBNL IEEE ETS")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>