[S390] add missing device put

The dasd_alias_show function does not return a device reference
in case the device is an alias.
Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd_devmap.c

@@ -948,9 +948,11 @@ static ssize_t dasd_alias_show(struct device *dev,
 	if (device->discipline && device->discipline->get_uid &&
 	    !device->discipline->get_uid(device, &uid)) {
 		if (uid.type == UA_BASE_PAV_ALIAS ||
-		    uid.type == UA_HYPER_PAV_ALIAS)
+		    uid.type == UA_HYPER_PAV_ALIAS) {
+			dasd_put_device(device);
 			return sprintf(buf, "1\n");
 		}
+	}
 	dasd_put_device(device);
 
 	return sprintf(buf, "0\n");