[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>
                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 {