serial: remove redundant tty_port_link_device()

The linking is done implicitly by tty_port_register_device_attr_serdev()
few lines below. So drop this explicit tty_port_link_device().

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/20250317070046.24386-26-jirislaby@kernel.org


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