net/mlx5: fix L3 VXLAN RSS expansion

net/mlx5: fix L3 VXLAN RSS expansion

The RSS expansion feature was introduced to split RSS flows according to
the adjustment between the RSS types and the flow items.

The expansion function gets an item tree for the above adjustment from
the caller which reflects the HW needs.

The standard vxlan header next protocol is always Ethernet while there
are some Mellanox customers who use their own method to allow L3
headers after the vxlan tunnel header.

The expansion tree of mlx5 PMD didn't expect to get L3 headers after the
vxlan header what caused a failure in flow creation when inner RSS is
requested on L3 after vxlan flow.

Add IPV4 and IPV6 as optional headers after vxlan in the RSS expansion
tree to allow L3 tunnel support for vxlan.

Fixes: f4f06e361516 ("net/mlx5: add flow VXLAN item")
Cc: stable@dpdk.org
Signed-off-by: Matan Azrad <matan@mellanox.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>