tgupdate: merge t/DO-NOT-MERGE-mptcp-enabled-by-default into t/upstream base

Author: matttbe

tools/testing/selftests/bpf/progs/read_cgroupfs_xattr.c

@@ -6,6 +6,7 @@
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_core_read.h>
 #include "bpf_experimental.h"
+#include "cgrp_kfunc_common.h"
 
 char _license[] SEC("license") = "GPL";