USB: serial: make remove callback return void

All usb_serial drivers return 0 in their remove callbacks and driver
core ignores the value returned by usb_serial_device_remove(). So change
the remove callback to return void and return 0 unconditionally in
usb_serial_device_remove().

Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Link: https://lore.kernel.org/r/20210208143149.963644-2-uwe@kleine-koenig.org
Signed-off-by: Johan Hovold <johan@kernel.org>
diff --git a/drivers/usb/serial/mos7720.c b/drivers/usb/serial/mos7720.c
index aa55169..701dfb3 100644
--- a/drivers/usb/serial/mos7720.c
+++ b/drivers/usb/serial/mos7720.c
@@ -1760,14 +1760,12 @@ static int mos7720_port_probe(struct usb_serial_port *port)
 	return 0;
 }
 
-static int mos7720_port_remove(struct usb_serial_port *port)
+static void mos7720_port_remove(struct usb_serial_port *port)
 {
 	struct moschip_port *mos7720_port;
 
 	mos7720_port = usb_get_serial_port_data(port);
 	kfree(mos7720_port);
-
-	return 0;
 }
 
 static struct usb_serial_driver moschip7720_2port_driver = {