drm/amd/display: Keep PHY active for DP displays on DCN31

[Why & How]
Port of a change that went into DCN314 to keep the PHY enabled
when we have a connected and active DP display.

The PHY can hang if PHY refclk is disabled inadvertently.

Cc: Mario Limonciello <mario.limonciello@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Reviewed-by: Josip Pavic <josip.pavic@amd.com>
Acked-by: Alan Liu <haoping.liu@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@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/clk_mgr/dcn31/dcn31_clk_mgr.c

@@ -87,6 +87,11 @@ static int dcn31_get_active_display_cnt_wa(
 				stream->signal == SIGNAL_TYPE_DVI_SINGLE_LINK ||
 				stream->signal == SIGNAL_TYPE_DVI_DUAL_LINK)
 			tmds_present = true;
+
+		/* Checking stream / link detection ensuring that PHY is active*/
+		if (dc_is_dp_signal(stream->signal) && !stream->dpms_off)
+			display_count++;
+
 	}
 
 	for (i = 0; i < dc->link_count; i++) {