If the sentinel triggers, we do not want the boot loader authors to
just poke it and make the error go away, we want them to actually fix
the problem.

This should help avoid making the incorrect change in non-compliant
bootloaders.

[ hpa: dropped the Documentation/x86/boot.txt hunk pending
  clarifications ]
Signed-off-by: Peter Jones <pjones@redhat.com>
Link: http://lkml.kernel.org/r/1362592823-28967-1-git-send-email-pjones@redhat.comSigned-off-by: H. Peter Anvin <hpa@zytor.com>