x86, hotplug: Use mwait to offline a processor, fix the legacy case

x86, hotplug: Use mwait to offline a processor, fix the legacy case

upstream ea53069231f9317062910d6e772cca4ce93de8c8
x86, hotplug: Use mwait to offline a processor, fix the legacy case

Here included also some small follow-on patches to the same code:

upstream a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a
x86, hotplug: Move WBINVD back outside the play_dead loop

upstream ce5f68246bf2385d6174856708d0b746dc378f20
x86, hotplug: In the MWAIT case of play_dead, CLFLUSH the cache line

https://bugzilla.kernel.org/show_bug.cgi?id=5471

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>