drm/amd/display: Fix black screen when disabling Freesync in OSD

[Why]
Black screen encountered when disabling Freesync through OSD on some
displays.

[How]
Set the should_disable flag when new top pipe has no plane state to
ensure that pipes get cleaned up.
Reviewed-by: NChris Park <Chris.Park@amd.com>
Acked-by: NSolomon Chiu <solomon.chiu@amd.com>
Signed-off-by: NIlya Bakoulin <Ilya.Bakoulin@amd.com>
Tested-by: NDaniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -1085,6 +1085,16 @@ static void disable_dangling_plane(struct dc *dc, struct dc_state *context)
 				dc->current_state->stream_count != context->stream_count)
 			should_disable = true;
 
+		if (old_stream && !dc->current_state->res_ctx.pipe_ctx[i].top_pipe) {
+			struct pipe_ctx *old_pipe, *new_pipe;
+
+			old_pipe = &dc->current_state->res_ctx.pipe_ctx[i];
+			new_pipe = &context->res_ctx.pipe_ctx[i];
+
+			if (old_pipe->plane_state && !new_pipe->plane_state)
+				should_disable = true;
+		}
+
 		if (should_disable && old_stream) {
 			dc_rem_all_planes_for_stream(dc, old_stream, dangling_context);
 			disable_all_writeback_pipes_for_stream(dc, old_stream, dangling_context);