iio: adc: mxs-lradc: Fix return value check in mxs_lradc_adc_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. Also add NULL test for iores.
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>

drivers/iio/adc/mxs-lradc-adc.c

@@ -718,9 +718,12 @@ static int mxs_lradc_adc_probe(struct platform_device *pdev)
 	adc->dev = dev;
 
 	iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!iores)
+		return -EINVAL;
+
 	adc->base = devm_ioremap(dev, iores->start, resource_size(iores));
-	if (IS_ERR(adc->base))
-		return PTR_ERR(adc->base);
+	if (!adc->base)
+		return -ENOMEM;
 
 	init_completion(&adc->completion);
 	spin_lock_init(&adc->lock);