drm/amd/display: Use SIGNAL_TYPE_NONE in disable_output unless eDP

[WHY]
Currently made a change where disable_output is called using signal_type.
Using actual signal_type when calilng disable_output in power_down_encoders
would make DP to HDMI dongle not light up on boot. As it would have signal_type
SIGNAL_TYPE_DISPLAY_PORT.

[HOW]
Set signal_type to SIGNAL_TYPE_NONE unless it is eDP.
Signed-off-by: Sung Lee <sung.lee@amd.com>
Reviewed-by: Yongqiang Sun <yongqiang.sun@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce110/dce110_hw_sequencer.c

@@ -1438,6 +1438,9 @@ static void power_down_encoders(struct dc *dc)
 			if (!dc->links[i]->wa_flags.dp_keep_receiver_powered)
 				dp_receiver_power_ctrl(dc->links[i], false);
 
+		if (signal != SIGNAL_TYPE_EDP)
+			signal = SIGNAL_TYPE_NONE;
+
 		dc->links[i]->link_enc->funcs->disable_output(
 				dc->links[i]->link_enc, signal);
 	}