x86: VMI fix

Jeff Chua bisected down a vmware guest boot breakage (hang) to
this paravirt change:

  commit 8d947344


  Author: Glauber de Oliveira Costa <gcosta@redhat.com>
  Date:   Wed Jan 30 13:31:12 2008 +0100

    x86: change write_idt_entry signature

fix the off-by-one indexing bug ...

Bisected-by: Jeff Chua <jeff.chua.linux@gmail.com>
Tested-by: Jeff Chua <jeff.chua.linux@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>