drivers: watchdog: exar_wdt.c fix use after free

fix use after free by storing the result of PTR_ERR(n->pdev)
to a local variable before returning.
Signed-off-by: Manank Patel <pmanank200502@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20221013095258.1424967-1-pmanank200502@gmail.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/exar_wdt.c

@@ -355,8 +355,10 @@ static int __init exar_wdt_register(struct wdt_priv *priv, const int idx)
 						    &priv->wdt_res, 1,
 						    priv, sizeof(*priv));
 	if (IS_ERR(n->pdev)) {
+		int err = PTR_ERR(n->pdev);
+
 		kfree(n);
-		return PTR_ERR(n->pdev);
+		return err;
 	}
 
 	list_add_tail(&n->list, &pdev_list);