x86, apic: clean up ->cpu_present_to_apicid()

- separate the namespace

 - remove macros

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/include/asm/genapic.h b/arch/x86/include/asm/genapic.h
index 38b1202..2cb14d5 100644
--- a/arch/x86/include/asm/genapic.h
+++ b/arch/x86/include/asm/genapic.h
@@ -108,6 +108,8 @@
 DECLARE_PER_CPU(int, x2apic_extra_bits);
 
 extern void default_setup_apic_routing(void);
+
+extern int default_cpu_present_to_apicid(int mps_cpu);
 #endif
 
 #endif /* _ASM_X86_GENAPIC_64_H */