net: lan966x: avoid unregistering netdev on register failure

net: lan966x: avoid unregistering netdev on register failure

lan966x_probe_port() stores the newly allocated net_device in the
port before calling register_netdev(). If register_netdev() fails,
the probe error path calls lan966x_cleanup_ports(), which sees
port->dev and calls unregister_netdev() for a device that was never
registered.

Destroy the phylink instance created for this port and clear port->dev
before returning the registration error. The common cleanup path now skips
ports without port->dev before reaching the registered netdev cleanup, so
it only handles ports that reached the registered-netdev lifetime.

This also avoids treating an uninitialized FDMA netdev and the failed port
as a NULL == NULL match in the common cleanup path.

Fixes: d28d6d2e37d1 ("net: lan966x: add port module support")
Co-developed-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Ijae Kim <ae878000@gmail.com>
Signed-off-by: Myeonghun Pak <mhun512@gmail.com>
Link: https://patch.msgid.link/20260506124331.31945-1-mhun512@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>