net: airoha: Rely on airoha_eth struct in airoha_ppe_flow_offload_cmd signature

net: airoha: Rely on airoha_eth struct in airoha_ppe_flow_offload_cmd signature

Rely on airoha_eth struct in airoha_ppe_flow_offload_cmd routine
signature and in all the called subroutines.
This is a preliminary patch to introduce flowtable offload for traffic
received by the wlan NIC and forwarded to the ethernet one.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250823-airoha-en7581-wlan-rx-offload-v3-1-f78600ec3ed8@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>