net: airoha: Add L2 hw acceleration support

net: airoha: Add L2 hw acceleration support

Similar to mtk driver, introduce the capability to offload L2 traffic
defining flower rules in the PSE/PPE engine available on EN7581 SoC.
Since the hw always reports L2/L3/L4 flower rules, link all L2 rules
sharing the same L2 info (with different L3/L4 info) in the L2 subflows
list of a given L2 PPE entry.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Link: https://patch.msgid.link/20250409-airoha-flowtable-l2b-v2-2-4a1e3935ea92@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>