x86-32: Allow UP/SMP lock replacement in cmpxchg64

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: Luca Barbieri <luca@luca-barbieri.com>
LKML-Reference: <1267005265-27958-3-git-send-email-luca@luca-barbieri.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/include/asm/cmpxchg_32.h

@@ -271,7 +271,8 @@ extern unsigned long long cmpxchg_486_u64(volatile void *, u64, u64);
 	__typeof__(*(ptr)) __ret;				\
 	__typeof__(*(ptr)) __old = (o);				\
 	__typeof__(*(ptr)) __new = (n);				\
-	alternative_io("call cmpxchg8b_emu",			\
+	alternative_io(LOCK_PREFIX_HERE				\
+			"call cmpxchg8b_emu",			\
 			"lock; cmpxchg8b (%%esi)" ,		\
 		       X86_FEATURE_CX8,				\
 		       "=A" (__ret),				\