Changes in the configuration could cause PSR to be compatible and
enabled so driver must also be able to disable DRRS when doing
fastsets.

v2: Fixed name of DRRS compute function (Anshuman)

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/209
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/173
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/209
Cc: Srinivas K <srinivasx.k@intel.com>
Cc: Hariom Pandey <hariom.pandey@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200825171331.17971-2-jose.souza@intel.com