net/mlx5e: XDP, Improve Striding RQ check with XDP

Non-linear mem scheme of Striding RQ does not yet support XDP at this
point. Take the check where it belongs, inside the params validation
function mlx5e_params_validate_xdp().

Reviewed-by: Gal Pressman <gal@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>