Use the functionality just introduced in the previous patch: mark the
lock prefixes in cmpxchg64 alternatives for UP removal.

Changes in v2:
- Naming change
Signed-off-by: NLuca Barbieri <luca@luca-barbieri.com>
LKML-Reference: <1267005265-27958-3-git-send-email-luca@luca-barbieri.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>