net/mlx5: Explicitly set scheduling element and TSAR type

Ensure the scheduling element type and TSAR type are explicitly
initialized in the QoS rate group creation.

This prevents potential issues due to default values.

Fixes: 1ae258f8 ("net/mlx5: E-switch, Introduce rate limiting groups API")
Signed-off-by: Carolina Jubran <cjubran@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>