IB/cm: Fix device_create() return value check

Use IS_ERR() instead of comparing to NULL.
Signed-off-by: NJani Nikula <ext-jani.1.nikula@nokia.com>
Signed-off-by: NRoland Dreier <rolandd@cisco.com>

drivers/infiniband/core/cm.c

@@ -3693,7 +3693,7 @@ static void cm_add_one(struct ib_device *ib_device)
 	cm_dev->device = device_create(&cm_class, &ib_device->dev,
 				       MKDEV(0, 0), NULL,
 				       "%s", ib_device->name);
-	if (!cm_dev->device) {
+	if (IS_ERR(cm_dev->device)) {
 		kfree(cm_dev);
 		return;
 	}