power/reset: at91: fix return value check in at91_reset_platform_probe()

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

Fixes: ecfe64d8c55f ("power: reset: Add AT91 reset driver")
Signed-off-by: Wei Yongjun <[e-mail]>
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/reset/at91-reset.c

···
 		res = platform_get_resource(pdev, IORESOURCE_MEM, idx + 1 );
 		at91_ramc_base[idx] = devm_ioremap(&pdev->dev, res->start,
 						   resource_size(res));
-		if (IS_ERR(at91_ramc_base[idx])) {
+		if (!at91_ramc_base[idx]) {
 			dev_err(&pdev->dev, "Could not map ram controller address\n");
-			return PTR_ERR(at91_ramc_base[idx]);
+			return -ENOMEM;
 		}
 	}