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

Current audio-graph-card2 can use Codec2Codec, and having its
original parameter (= rate) on DT is mandatory for now.

But simple-card-utils.c has asoc_simple_init_for_codec2codec() to
setup *default* Codec2Codec settings.

This patch makes Audio Graph Card2 Codec2Codec rate settings
optional.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://lore.kernel.org/r/87fsjls95u.wl-kuninori.morimoto.gx@renesas.com


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