tools/liblockdep: add userspace versions of WRITE_ONCE and RCU_INIT_POINTER

These were added to the kernel code in cee34d88 ("lockdep: Fix a race between
/proc/lock_stat and module unload"). There's nothing special we need to do
about them in userspace.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>