drm/amd/display: Add registry for mem pwr control

[What]
Need debug options to control lightl/deep sleep
[How]
Add registry for memory power control
Signed-off-by: Braden Bakker <Braden.Bakker@amd.com>
Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dc.h

@@ -390,6 +390,7 @@ struct dc_debug_options {
 	int always_scale;
 	bool disable_pplib_clock_request;
 	bool disable_clock_gate;
+	bool disable_mem_low_power;
 	bool disable_dmcu;
 	bool disable_psr;
 	bool force_abm_enable;