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>

arch/x86/kernel/apic/summit_32.c

@@ -551,5 +551,4 @@ struct apic apic_summit = {
 	.safe_wait_icr_idle		= native_safe_apic_wait_icr_idle,
 
 	.x86_32_early_logical_apicid	= summit_early_logical_apicid,
-	.x86_32_numa_cpu_node		= default_x86_32_numa_cpu_node,
 };