[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>
diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
index 34d51dd..bed7b46 100644
--- a/drivers/s390/block/dasd_devmap.c
+++ b/drivers/s390/block/dasd_devmap.c
@@ -948,8 +948,10 @@
 	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);