Adding an overview of DRRS in general and the implementation for eDP DRRS.
Also, describing the functions related to eDP DRRS.
Signed-off-by: NVandana Kannan <vandana.kannan@intel.com>
Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>