Although only used currently for tcp sockets, this function
is now used in common sock code (for sock_clone())
Commit 475f1b52645a29936b9df1d8fcd45f7e56bd4a9f moved the
declaration of sock_update_clone() to inside sock.c, but
this only fixes the problem when CONFIG_CGROUP_MEM_RES_CTLR_KMEM
is also not defined.
This patch here is verified to fix both problems, although
reverting the previous one is not necessary.