net: airoha: ppe: Disable packet keepalive

Since netfilter flowtable entries are now refreshed by flow-stats
polling, we can disable hw packet keepalive used to periodically send
packets belonging to offloaded flows to the kernel in order to refresh
flowtable entries.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250516-airoha-en7581-flowstats-v2-3-06d5fbf28984@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>