ASoC: audio-graph-card2.c: make Codec2Codec settings optional

Merge series from Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>:

Audio Graph Card2 has Codec2Codec support, but I noticed
 - Current Codec2Codec setting value is not correct
   because it is using of_get_property().
 - simple-card-utils has default Codec2Codec settings
   and it is overwriting Card2 settings
 - This default settings works for non Codec2Codec case
   (= DPCM::BE case) too.

This patch-set solve these issues.