ASoC: rsrc-card: tidyup dai format for DPCM

rsrc-card is DPCM supported version of simple-card. Thus it has similar
DT format. OTOH, snd_soc_dai_link requests cpu/codec, but one of them
will be snd-soc-dummy in DPCM case, and DPCM requests frontend/backend
dai_link. This means it might have multi backend/codec.
And, SND_SOC_DAIFMT_xxx is based on "codec". Because of these
difference, current rsrc card can't detect correct dai_fmt.
This patch detect correct dai fmt from 1st "codec".

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>