gpio: mockup: remove unneeded return statement

There's a return; at the end of a void function. This is not needed so
remove it.
Signed-off-by: NBartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/gpio/gpio-mockup.c

@@ -372,8 +372,6 @@ static void gpio_mockup_debugfs_setup(struct device *dev,
 		debugfs_create_file(name, 0200, chip->dbg_dir, priv,
 				    &gpio_mockup_debugfs_ops);
 	}
-
-	return;
 }
 
 static int gpio_mockup_name_lines(struct device *dev,