ipmi: Fix ioremap error handling in bt-bmc

devm_ioremap_resource returns ERR_PTR so we can't check for NULL.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Acked-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/bt-bmc.c

@@ -438,8 +438,8 @@ static int bt_bmc_probe(struct platform_device *pdev)
 	}
 
 	bt_bmc->base = devm_ioremap_resource(&pdev->dev, res);
-	if (!bt_bmc->base)
-		return -ENOMEM;
+	if (IS_ERR(bt_bmc->base))
+		return PTR_ERR(bt_bmc->base);
 
 	mutex_init(&bt_bmc->mutex);
 	init_waitqueue_head(&bt_bmc->queue);