usb: chipidea: fix return value check in ci_hdrc_pci_probe()

In case of error, the function usb_phy_generic_register()
returns ERR_PTR() and never returns NULL. The NULL test in
the return value check should be replaced with IS_ERR().
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: NPeter Chen <peter.chen@nxp.com>

drivers/usb/chipidea/ci_hdrc_pci.c

@@ -85,8 +85,8 @@ static int ci_hdrc_pci_probe(struct pci_dev *pdev,
 
 	/* register a nop PHY */
 	ci->phy = usb_phy_generic_register();
-	if (!ci->phy)
-		return -ENOMEM;
+	if (IS_ERR(ci->phy))
+		return PTR_ERR(ci->phy);
 
 	memset(res, 0, sizeof(res));
 	res[0].start	= pci_resource_start(pdev, 0);