x86: Fix atomic64_xxx_cx8() functions

It appears about all functions in arch/x86/lib/atomic64_cx8_32.S
are wrong in case cmpxchg8b must be restarted, because
LOCK_PREFIX macro defines a label "1" clashing with other local
labels :

1:
	some_instructions
	LOCK_PREFIX
	cmpxchg8b (%ebp)
	jne 1b  / jumps to beginning of LOCK_PREFIX !

A possible fix is to use a magic label "672" in LOCK_PREFIX asm
definition, similar to the "671" one we defined in
LOCK_PREFIX_HERE.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Jan Beulich <JBeulich@suse.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1325608540.2320.103.camel@edumazet-HP-Compaq-6005-Pro-SFF-PCSigned-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/include/asm/alternative-asm.h

@@ -4,10 +4,10 @@
 
 #ifdef CONFIG_SMP
 	.macro LOCK_PREFIX
-1:	lock
+672:	lock
 	.section .smp_locks,"a"
 	.balign 4
-	.long 1b - .
+	.long 672b - .
 	.previous
 	.endm
 #else