net/mlx5: validate flow rule item order

net/mlx5: validate flow rule item order

The Item order validation between L2 and L3 is missing, which leading to
the following flow rule is accepted:

  testpmd> flow create 0 ingress pattern ipv4 / eth / end actions drop /
           end

Only the outer L3 layer should check whether the L2 layer is present,
because the L3 layer could directly follow the tunnel layer
without L2 layer.

Meanwhile inner L2 layer should check whether there is inner L3 layer
before it.

Fixes: 23c1d42c7138 ("net/mlx5: split flow validation to dedicated function")
Cc: stable@dpdk.org
Signed-off-by: Xiaoyu Min <jackmin@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>