USB: gadget: udc: s3c2410_udc: fix return value check in s3c2410_udc_probe()

In case of error, the function devm_platform_ioremap_resource()
returns ERR_PTR() and never returns NULL. The NULL test in the
return value check should be replaced with IS_ERR().

Fixes: 188db4435ac6 ("usb: gadget: s3c: use platform resources")
Cc: stable <[e-mail]>
Reported-by: Hulk Robot <[e-mail]>
Reviewed-by: Arnd Bergmann <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Wei Yongjun <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/udc/s3c2410_udc.c

···
 	udc_info = dev_get_platdata(&pdev->dev);
 
 	base_addr = devm_platform_ioremap_resource(pdev, 0);
-	if (!base_addr) {
-		retval = -ENOMEM;
+	if (IS_ERR(base_addr)) {
+		retval = PTR_ERR(base_addr);
 		goto err_mem;
 	}