drm/amd/display: Fixed using wrong eDP power sequence function pointer

[why]
dc->hwss->edp_backlight_control is null, it would casue it only be off
main-link of eDP.  It is not worng behavior for eDP power sequence off.

[how]
Must use hwseq->funcs.edp_backlight_control finction pointer for edp
backlight.
Signed-off-by: Yi-Ling Chen <Yi-Ling.Chen2@amd.com>
Reviewed-by: Sung Lee <Sung.Lee@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/dcn10/dcn10_hw_sequencer.c

@@ -1394,10 +1394,10 @@ void dcn10_init_hw(struct dc *dc)
 		if (edp_link &&
 				edp_link->link_enc->funcs->is_dig_enabled &&
 				edp_link->link_enc->funcs->is_dig_enabled(edp_link->link_enc) &&
-				dc->hwss.edp_backlight_control &&
+				dc->hwseq->funcs.edp_backlight_control &&
 				dc->hwss.power_down &&
 				dc->hwss.edp_power_control) {
-			dc->hwss.edp_backlight_control(edp_link, false);
+			dc->hwseq->funcs.edp_backlight_control(edp_link, false);
 			dc->hwss.power_down(dc);
 			dc->hwss.edp_power_control(edp_link, false);
 		} else {