net: airoha: Delay offloading until all net_devices are fully registered

net: airoha: Delay offloading until all net_devices are fully registered

Netfilter flowtable can theoretically try to offload flower rules as soon
as a net_device is registered while all the other ones are not
registered or initialized, triggering a possible NULL pointer dereferencing
of qdma pointer in airoha_ppe_set_cpu_port routine. Moreover, if
register_netdev() fails for a particular net_device, there is a small
race if Netfilter tries to offload flowtable rules before all the
net_devices are properly unregistered in airoha_probe() error patch,
triggering a NULL pointer dereferencing in airoha_ppe_set_cpu_port
routine. In order to avoid any possible race, delay offloading until
all net_devices are registered in the networking subsystem.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260329-airoha-regiser-race-fix-v2-1-f4ebb139277b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>