fscache: add missing unlock

Sparse complained about this missing spin_unlock()
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fscache/page.c

@@ -881,6 +881,7 @@ submit_failed:
 	goto nobufs;
 
 nobufs_unlock_obj:
+	spin_unlock(&cookie->stores_lock);
 	spin_unlock(&object->lock);
 nobufs:
 	spin_unlock(&cookie->lock);