x86/mcheck: convert to hotplug state engine, take #2

From: Sebastian Andrzej Siewior
Date: Thu Nov 10 2016 - 12:46:31 EST


The fixed up version of patch 1-4 was already posted and are here just for
completeness.
Patches 5-7 are new and address Boris's concern not to init the MCE feature too
late on the boot CPU during the boot process.

Sebastian