mmc: jz4740: fix return value check in jz4740_mmc_probe()

In case of error, the function devm_ioremap_resource() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check should
be replaced with IS_ERR(). Also there is already a error message within
devm_ioremap_resource(), so remove the dev_err call to avoid redundant
error message.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/jz4740_mmc.c

@@ -783,9 +783,8 @@ static int jz4740_mmc_probe(struct platform_device* pdev)
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	host->base = devm_ioremap_resource(&pdev->dev, res);
-	if (!host->base) {
-		ret = -EBUSY;
-		dev_err(&pdev->dev, "Failed to ioremap base memory\n");
+	if (IS_ERR(host->base)) {
+		ret = PTR_ERR(host->base);
 		goto err_free_host;
 	}