drm/amd/display: Fix lightup regression with DP2 single display configs

[WHY]
Previous fix for multiple displays downstream of DP2 MST hub caused regression

[HOW]
Match sink IDs instead of sink struct addresses
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Charlene Liu <charlene.liu@amd.com>
Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Michael Strauss <michael.strauss@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/dml2/dml2_utils.c

@@ -161,6 +161,14 @@ bool is_dp2p0_output_encoder(const struct pipe_ctx *pipe_ctx)
 	if (pipe_ctx->stream == NULL)
 		return false;
 
+	/* Count MST hubs once by treating only 1st remote sink in topology as an encoder */
+	if (pipe_ctx->stream->link && pipe_ctx->stream->link->remote_sinks[0]) {
+		return (pipe_ctx->stream_res.hpo_dp_stream_enc &&
+			pipe_ctx->link_res.hpo_dp_link_enc &&
+			dc_is_dp_signal(pipe_ctx->stream->signal) &&
+			(pipe_ctx->stream->link->remote_sinks[0]->sink_id == pipe_ctx->stream->sink->sink_id));
+	}
+
 	return (pipe_ctx->stream_res.hpo_dp_stream_enc &&
 		pipe_ctx->link_res.hpo_dp_link_enc &&
 		dc_is_dp_signal(pipe_ctx->stream->signal));