net: ethernet: ti: am65-cpsw-nuss: populate netdev of_node

So that of_find_net_device_by_node() can find cpsw-nuss ports and other DSA
switches can be stacked downstream.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
Link: https://lore.kernel.org/r/20240528075954.3608118-3-alexander.sverdlin@siemens.com


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