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/kernel/genx2apic_cluster.c b/arch/x86/kernel/genx2apic_cluster.c
index 2eeca6e..710d612 100644
--- a/arch/x86/kernel/genx2apic_cluster.c
+++ b/arch/x86/kernel/genx2apic_cluster.c
@@ -199,7 +199,7 @@
 	.multi_timer_check		= NULL,
 	.apicid_to_node			= NULL,
 	.cpu_to_logical_apicid		= NULL,
-	.cpu_present_to_apicid		= NULL,
+	.cpu_present_to_apicid		= default_cpu_present_to_apicid,
 	.apicid_to_cpu_present		= NULL,
 	.setup_portio_remap		= NULL,
 	.check_phys_apicid_present	= NULL,