net/mlx5e: Fix the value of MLX5E_MAX_RQ_NUM_MTTS

MLX5E_MAX_RQ_NUM_MTTS should be the maximum value, so that
MLX5_MTT_OCTW(MLX5E_MAX_RQ_NUM_MTTS) fits into u16. The current value of
1 << 17 results in MLX5_MTT_OCTW(1 << 17) = 1 << 16, which doesn't fit
into u16. This commit replaces it with the maximum value that still
fits u16.

Fixes: 73281b78 ("net/mlx5e: Derive Striding RQ size from MTU")
Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>