tty: do not check tty_unregister_driver's return value

These drivers check tty_unregister_driver return value. But they don't
handle a failure correctly (they free the driver in any case). So stop
checking tty_unregister_driver return value and remove also the prints.

In the next patch, tty_unregister_driver's return type will be switched
to void.

Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-xtensa@linux-xtensa.org
Cc: Jiri Kosina <jikos@kernel.org>
Cc: David Sterba <dsterba@suse.com>
Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: David Sterba <dsterba@suse.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210302062214.29627-34-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
index 6441737..4727a41 100644
--- a/drivers/tty/synclink_gt.c
+++ b/drivers/tty/synclink_gt.c
@@ -3705,7 +3705,6 @@ static const struct tty_operations ops = {
 
 static void slgt_cleanup(void)
 {
-	int rc;
 	struct slgt_info *info;
 	struct slgt_info *tmp;
 
@@ -3714,9 +3713,7 @@ static void slgt_cleanup(void)
 	if (serial_driver) {
 		for (info=slgt_device_list ; info != NULL ; info=info->next_device)
 			tty_unregister_device(serial_driver, info->line);
-		rc = tty_unregister_driver(serial_driver);
-		if (rc)
-			DBGERR(("tty_unregister_driver error=%d\n", rc));
+		tty_unregister_driver(serial_driver);
 		put_tty_driver(serial_driver);
 	}