usb: gadget: remove leaked entry from udc driver list

The usb_add_gadget_udc will add a new gadget to the udc class
driver list. Not calling usb_del_gadget_udc in error branch
will result in residual gadget entry in the udc driver list.
We fix it by calling usb_del_gadget_udc to clean it when error
return.

Fixes: 48ba02b2 ("usb: gadget: add udc driver for max3420")
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Zhang Qilong <zhangqilong3@huawei.com>
Link: https://lore.kernel.org/r/20210727073142.84666-1-zhangqilong3@huawei.com
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/udc/max3420_udc.c

@@ -1255,12 +1255,14 @@ static int max3420_probe(struct spi_device *spi)
 	err = devm_request_irq(&spi->dev, irq, max3420_irq_handler, 0,
 			       "max3420", udc);
 	if (err < 0)
-		return err;
+		goto del_gadget;
 
 	udc->thread_task = kthread_create(max3420_thread, udc,
 					  "max3420-thread");
-	if (IS_ERR(udc->thread_task))
-		return PTR_ERR(udc->thread_task);
+	if (IS_ERR(udc->thread_task)) {
+		err = PTR_ERR(udc->thread_task);
+		goto del_gadget;
+	}
 
 	irq = of_irq_get_byname(spi->dev.of_node, "vbus");
 	if (irq <= 0) { /* no vbus irq implies self-powered design */
@@ -1280,10 +1282,14 @@ static int max3420_probe(struct spi_device *spi)
 		err = devm_request_irq(&spi->dev, irq,
 				       max3420_vbus_handler, 0, "vbus", udc);
 		if (err < 0)
-			return err;
+			goto del_gadget;
 	}
 
 	return 0;
+
+del_gadget:
+	usb_del_gadget_udc(&udc->gadget);
+	return err;
 }
 
 static int max3420_remove(struct spi_device *spi)