intel_idle: Revert change of auto_demotion_disable_flags for Nehalem

Commit b66b8b9a ('intel-idle: convert
to x86_cpu_id auto probing') added a distinction between Nehalem and
Westemere processors and changed auto_demotion_disable_flags for the
former to 0.  This was not explained in the commit message, so change
it back.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Thomas Renninger <trenn@suse.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>