ASoC: soc-topology.c: add comment for Platform/Codec

Not only Platform but Codec also might be overwritten on Topology.
This patch adds comment about it not to use asoc_dummy_dlc here.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87sfcqyphq.wl-kuninori.morimoto.gx@renesas.com


Signed-off-by: Mark Brown <broonie@kernel.org>