x86, numa: Fix CONFIG_DEBUG_PER_CPU_MAPS without NUMA emulation

"x86, numa: Fake node-to-cpumask for NUMA emulation" broke the
build when CONFIG_DEBUG_PER_CPU_MAPS is set and CONFIG_NUMA_EMU
is not.  This is because it is possible to map a cpu to multiple
nodes when NUMA emulation is used; the patch required a physical
node address table to find those nodes that was only available
when CONFIG_NUMA_EMU was enabled.

This extracts the common debug functionality to its own function
for CONFIG_DEBUG_PER_CPU_MAPS and uses it regardless of whether
CONFIG_NUMA_EMU is set or not.

NUMA emulation will now iterate over the set of possible nodes
for each cpu and call the new debug function whereas only the
cpu's node will be used without NUMA emulation enabled.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <alpine.DEB.2.00.1012301053590.12995@chino.kir.corp.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>