usb: gadget: udc: renesas_usb3: should fail if devm_phy_get() returns error

This patch fixes an issue that this driver ignores errors other than
the non-existence of the device, f.e. a memory allocation failure
in devm_phy_get(). So, this patch replaces devm_phy_get() with
devm_phy_optional_get().
Reported-by: Simon Horman <horms+renesas@verge.net.au>
Fixes: 279d4bc6 ("usb: gadget: udc: renesas_usb3: add support for generic phy")
Cc: <stable@vger.kernel.org> # v4.15+
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/udc/renesas_usb3.c

@@ -2638,9 +2638,11 @@ static int renesas_usb3_probe(struct platform_device *pdev)
 	 * This is optional. So, if this driver cannot get a phy,
 	 * this driver will not handle a phy anymore.
 	 */
-	usb3->phy = devm_phy_get(&pdev->dev, "usb");
-	if (IS_ERR(usb3->phy))
-		usb3->phy = NULL;
+	usb3->phy = devm_phy_optional_get(&pdev->dev, "usb");
+	if (IS_ERR(usb3->phy)) {
+		ret = PTR_ERR(usb3->phy);
+		goto err_add_udc;
+	}
 
 	pm_runtime_enable(&pdev->dev);
 	ret = usb_add_gadget_udc(&pdev->dev, &usb3->gadget);