Btrfs: fix memory leak for name_cache in send/receive

When everything is done, name_cache_free is called which however
forgot to call kfree on the cache entries.
Signed-off-by: Alexander Block <ablock84@googlemail.com>

fs/btrfs/send.c

@@ -1822,6 +1822,7 @@ static void name_cache_free(struct send_ctx *sctx)
 
 	list_for_each_entry_safe(nce, tmp, &sctx->name_cache_list, list) {
 		name_cache_delete(sctx, nce);
+		kfree(nce);
 	}
 }