phy: qualcomm: fix return value check in qcom_ipq806x_usb_phy_probe()

In case of error, the function devm_ioremap() returns NULL pointer not
ERR_PTR(). The IS_ERR() test in the return value check should be
replaced with NULL test.

Fixes: ef19b11 ("phy: qualcomm: add qcom ipq806x dwc usb phy driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20200723113622.136752-1-weiyongjun1@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/qualcomm/phy-qcom-ipq806x-usb.c

@@ -505,9 +505,9 @@ static int qcom_ipq806x_usb_phy_probe(struct platform_device *pdev)
 	size = resource_size(res);
 	phy_dwc3->base = devm_ioremap(phy_dwc3->dev, res->start, size);
 
-	if (IS_ERR(phy_dwc3->base)) {
+	if (!phy_dwc3->base) {
 		dev_err(phy_dwc3->dev, "failed to map reg\n");
-		return PTR_ERR(phy_dwc3->base);
+		return -ENOMEM;
 	}
 
 	phy_dwc3->ref_clk = devm_clk_get(phy_dwc3->dev, "ref");