net/mlx5e: Use page-sized fragments with XDP multi buffer

The implementation of XDP in mlx5e assumes that the frame size is equal
to the page size. Force this limitation in the non-linear mode for XDP
multi buffer.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>