net: mdio: thunder: switch to scoped device_for_each_child_node()

There has already been an issue with the handling of early exits from
device_for_each_child() in this driver, and it was solved with commit
b1de5c78 ("net: mdio: thunder: Add missing fwnode_handle_put()") by
adding a call to fwnode_handle_put() right after the loop.

That solution is valid indeed, but if a new error path with a 'return'
is added to the loop, this solution will fail. A more secure approach
is using the scoped variant of the macro, which automatically
decrements the refcount of the child node when it goes out of scope,
removing the need for explicit calls to fwnode_handle_put().

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://patch.msgid.link/20240930-net-device_for_each_child_node_scoped-v2-1-35f09333c1d7@gmail.com


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