x86: clean up apic->apic_id_registered() methods

Impact: cleanup

x86 subarchitectures each defined a "apic_id_registered()" method,
which could be an inline function depending on which subarch we build
for, and which was also the name of a genapic field.

Untangle this namespace spaghetti by giving each of the instances
a separate name.

Also remove wrapper macro obfuscation.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mach-generic/bigsmp.c b/arch/x86/mach-generic/bigsmp.c
index 22c3608..17abf5c 100644
--- a/arch/x86/mach-generic/bigsmp.c
+++ b/arch/x86/mach-generic/bigsmp.c
@@ -62,7 +62,7 @@
 	.name				= "bigsmp",
 	.probe				= probe_bigsmp,
 	.acpi_madt_oem_check		= NULL,
-	.apic_id_registered		= apic_id_registered,
+	.apic_id_registered		= bigsmp_apic_id_registered,
 
 	.int_delivery_mode		= INT_DELIVERY_MODE,
 	.int_dest_mode			= INT_DEST_MODE,