x86, NUMA: Unify 32/64bit numa_cpu_node() implementation

Currently, the only meaningful user of apic->x86_32_numa_cpu_node() is
NUMAQ which returns valid mapping only after CPU is initialized during
SMP bringup; thus, the previous patch to set apicid -> node in
setup_local_APIC() makes __apicid_to_node[] always contain the correct
mapping whether custom apic->x86_32_numa_cpu_node() is used or not.

So, there is no reason to keep separate 32bit implementation.  We can
always consult __apicid_to_node[].  Move 64bit implementation from
numa_64.c to numa.c and remove 32bit implementation from numa_32.c.

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>