drm/amd/display: Fix plug/unplug external monitor will hang while playback MPO video

[Why]
Pipes for MPO primary and overlay will be power down and power up during
plug/unplug external monitor while MPO video playback.
But the pipes were the same after plug/unplug and should not need to be
power down and power up or it will make page flip interrupt disabled and
cause hang issue.

[How]
Add pipe split change condition that not only check the top pipe pointer
but also check the index of top pipe if both top pipes are available.
Reviewed-by: Sun peng Li <Sunpeng.Li@amd.com>
Acked-by: Brian Chang <Brian.Chang@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>

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

@@ -1074,8 +1074,15 @@ static void disable_dangling_plane(struct dc *dc, struct dc_state *context)
 		struct dc_stream_state *old_stream =
 				dc->current_state->res_ctx.pipe_ctx[i].stream;
 		bool should_disable = true;
-		bool pipe_split_change =
-			context->res_ctx.pipe_ctx[i].top_pipe != dc->current_state->res_ctx.pipe_ctx[i].top_pipe;
+		bool pipe_split_change = false;
+
+		if ((context->res_ctx.pipe_ctx[i].top_pipe) &&
+			(dc->current_state->res_ctx.pipe_ctx[i].top_pipe))
+			pipe_split_change = context->res_ctx.pipe_ctx[i].top_pipe->pipe_idx !=
+				dc->current_state->res_ctx.pipe_ctx[i].top_pipe->pipe_idx;
+		else
+			pipe_split_change = context->res_ctx.pipe_ctx[i].top_pipe !=
+				dc->current_state->res_ctx.pipe_ctx[i].top_pipe;
 
 		for (j = 0; j < context->stream_count; j++) {
 			if (old_stream == context->streams[j]) {