Add support for Dynamic Power Switching (DPS) for the RX51 board.

These scripts are still a work-in-progress. I'll keep sending patches to
update the scripts as they are optimised.
Signed-off-by: Amit Kucheria <amit.kucheria@verdurent.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>