tty_port: make tty_port_register_device wrap tty_port_register_device_attr

tty_register_device is just a wrapper for tty_register_device_attr with
NULL passed for drvdata and attr_grp. So similarly make
tty_port_register_device a wrapper of tty_port_register_device_attr so that
additions don't have to be made in both functions.
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/tty_port.c

@@ -67,8 +67,7 @@ struct device *tty_port_register_device(struct tty_port *port,
 		struct tty_driver *driver, unsigned index,
 		struct device *device)
 {
-	tty_port_link_device(port, driver, index);
-	return tty_register_device(driver, index, device);
+	return tty_port_register_device_attr(port, driver, index, device, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(tty_port_register_device);