drm/amd/display: Check disable_fec flag before enabling fec.

[Why]
dc debug option disable_fec was not working.

[How]
Check dc debug option disable_fec flag before
enabling fec in dp_should_enable_fec().

Reviewed-by: Wenjing Liu <wenjing.liu@amd.com>
Signed-off-by: Meenakshikumar Somasundaram <meenakshikumar.somasundaram@amd.com>
Signed-off-by: Tom Chung <chiahsuan.chung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Meenakshikumar Somasundaram

drivers/gpu/drm/amd/display/dc/link/protocols/link_dp_capability.c

@@ -357,7 +357,9 @@ bool dp_should_enable_fec(const struct dc_link *link)
 {
 	bool force_disable = false;
 
-	if (link->fec_state == dc_link_fec_enabled)
+	if (link->dc->debug.disable_fec)
+		force_disable = true;
+	else if (link->fec_state == dc_link_fec_enabled)
 		force_disable = false;
 	else if (link->connector_signal != SIGNAL_TYPE_DISPLAY_PORT_MST &&
 			link->local_sink &&