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/include/asm/bigsmp/apic.h b/arch/x86/include/asm/bigsmp/apic.h
index d8dd9f5..42c56df 100644
--- a/arch/x86/include/asm/bigsmp/apic.h
+++ b/arch/x86/include/asm/bigsmp/apic.h
@@ -4,9 +4,9 @@
 #define xapic_phys_to_log_apicid(cpu) (per_cpu(x86_bios_cpu_apicid, cpu))
 #define esr_disable (1)
 
-static inline int apic_id_registered(void)
+static inline int bigsmp_apic_id_registered(void)
 {
-	return (1);
+	return 1;
 }
 
 static inline const cpumask_t *target_cpus(void)