Flow label is defined as u32 in the in ipv6 flow spec, but
used internally in the flow specs parsing as u8. That was
causing loss of part of flow_label value.

Fixes: 2d1e697e ('IB/mlx5: Add support to match inner packet fields')
Reviewed-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Daria Velikovsky <daria@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>