x86-64: add "local_apic_timer_c2_ok" here too

Needed for any architecture that claims ARCH_APICTIMER_STOPS_ON_C3,
not just i386.

I'm hoping Thomas will clean this up a bit later..

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-x86_64/apic.h b/include/asm-x86_64/apic.h
index e81d0f2..7cfb39c 100644
--- a/include/asm-x86_64/apic.h
+++ b/include/asm-x86_64/apic.h
@@ -102,5 +102,6 @@
 #define ARCH_APICTIMER_STOPS_ON_C3	1
 
 extern unsigned boot_cpu_id;
+extern int local_apic_timer_c2_ok;
 
 #endif /* __ASM_APIC_H */