x86-32, NUMA: Make apic->x86_32_numa_cpu_node() optional

NUMAQ is the only meaningful user of this callback and
setup_local_APIC() the only callsite.  Stop torturing everyone else by
making the callback optional and removing all the boilerplate
implementations and assignments.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 2b7d573..a0c46f0 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -363,7 +363,12 @@
 	 */
 	int (*x86_32_early_logical_apicid)(int cpu);
 
-	/* determine CPU -> NUMA node mapping */
+	/*
+	 * Optional method called from setup_local_APIC() after logical
+	 * apicid is guaranteed to be known to initialize apicid -> node
+	 * mapping if NUMA initialization hasn't done so already.  Don't
+	 * add new users.
+	 */
 	int (*x86_32_numa_cpu_node)(int cpu);
 #endif
 };
@@ -537,8 +542,6 @@
 	return cpuid_apic >> index_msb;
 }
 
-extern int default_x86_32_numa_cpu_node(int cpu);
-
 #endif
 
 static inline unsigned int