net/mlx5e: Allow only complete TXQs partition in MQPRIO channel mode

Do not allow configurations of MQPRIO channel mode that do not
fully define and utilize the channels txqs.

Fixes: ec60c458 ("net/mlx5e: Support MQPRIO channel mode")
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>