serial: core: fix OF node leak

Make sure to drop the OF node reference taken when initialising the
control and port devices when the devices are later released.

Fixes: d36f0e9a ("serial: core: restore of_node information in sysfs")
Cc: Aidan Stewart <astewart@tektelic.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20250708085817.16070-1-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>