target-i386: Move hyperv_* static globals to X86CPU

- since hyperv_* helper functions are used only in target-i386/kvm.c
  move them there as static helpers

Requested-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>