drm/amd/display: add function for eDP and backlight power on

[HOW&WHY]
Add function to be used for early eDP power on
Reviewed-by: Anthony Koo <Anthony.Koo@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Evgenii Krasnikov <Evgenii.Krasnikov@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c

@@ -6360,3 +6360,14 @@ bool is_dp_128b_132b_signal(struct pipe_ctx *pipe_ctx)
 			dc_is_dp_signal(pipe_ctx->stream->signal));
 }
 #endif
+
+void edp_panel_backlight_power_on(struct dc_link *link)
+{
+	if (link->connector_signal != SIGNAL_TYPE_EDP)
+		return;
+
+	link->dc->hwss.edp_power_control(link, true);
+	link->dc->hwss.edp_wait_for_hpd_ready(link, true);
+	if (link->dc->hwss.edp_backlight_control)
+		link->dc->hwss.edp_backlight_control(link, true);
+}

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

@@ -217,4 +217,5 @@ bool is_dp_128b_132b_signal(struct pipe_ctx *pipe_ctx);
 void reset_dp_hpo_stream_encoders_for_link(struct dc_link *link);
 
 bool dp_retrieve_lttpr_cap(struct dc_link *link);
+void edp_panel_backlight_power_on(struct dc_link *link);
 #endif /* __DC_LINK_DP_H__ */