usb: gadget: udc: at91: use PTR_ERR_OR_ZERO()

coccicheck found this pattern which could be
converted to PTR_ERR_OR_ZERO(). No functional
changes.
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/at91_udc.c

@@ -1726,10 +1726,7 @@ static int at91sam9261_udc_init(struct at91_udc *udc)
 
 	udc->matrix = syscon_regmap_lookup_by_phandle(udc->pdev->dev.of_node,
 						      "atmel,matrix");
-	if (IS_ERR(udc->matrix))
-		return PTR_ERR(udc->matrix);
-
-	return 0;
+	return PTR_ERR_OR_ZERO(udc->matrix);
 }
 
 static void at91sam9261_udc_pullup(struct at91_udc *udc, int is_on)