net/mlx5: fix matcher priority with ICMP or ICMPv6

net/mlx5: fix matcher priority with ICMP or ICMPv6

On TCP/IP-based layered network, ICMP is considered and implemented
as part of layer 3 IP protocol. Actually, it is a user of the IP
protocol and must be encapsulated within IP packets. There is no
layer 4 protocol over ICMP.

The rule with layer 4 should be matched prior to the rule only with
layer 3 pattern when:
  1. Both rules are created in the same table
  2. Both rules could be hit
  3. The rules has the same priority

The steering result of the packet is indeterministic if there are
rules with patterns IP and IP+ICMP in the same table with the same
priority. Like TCP / UDP, a packet should hit the rule with a longer
matching criterion.

By treating the priority of ICMP/ICMPv6 as a layer 4 priority in the
PMD internally, the IP+ICMP will be hit in prior to IP only.

Fixes: d53aa89aea91 ("net/mlx5: support matching on ICMP/ICMP6")
Cc: stable@dpdk.org
Signed-off-by: Bing Zhao <bingz@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>