intel_menlow: don't set max_state a negative value

max_state is unsigned long.
don't set max_state a negative value

Cc : Thomas Sujith <sujith.thomas@intel.com>
Cc : Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>