x86/cpu: Move leftover contents of topology.c to setup.c

The only useful piece of arch/x86/kernel/topology.c is the definition
of arch_cpu_is_hotpluggable() that can be moved elsewhere (other
architectures tend to put it into setup.c), so do that and delete
the rest of the file.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/12422874.O9o76ZdvQC@kreacher