dm snapshot: use uninitialized_var

drivers/md/dm-exception-store.c: In function 'persistent_read_metadata':
drivers/md/dm-exception-store.c:452: warning: 'new_snapshot' may be used uninitialized in this function

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-exception-store.c

@@ -449,7 +449,7 @@ static void persistent_destroy(struct exception_store *store)
 
 static int persistent_read_metadata(struct exception_store *store)
 {
-	int r, new_snapshot;
+	int r, uninitialized_var(new_snapshot);
 	struct pstore *ps = get_info(store);
 
 	/*