powerpc/numa: remove ability to enable topology updates

Remove the /proc/powerpc/topology_updates interface and the
topology_updates=on/off command line argument. The internal
topology_updates_enabled flag remains for now, but always false.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200612051238.1007764-4-nathanl@linux.ibm.com