ASoC: simple-scu-card: use cpu/codec pointer on graph_dai_props

In  DPCM case, it uses CPU-dummy / dummy-Codec dai links, and
non DPCM case, it uses CPU-Codec dai links.

Now, we want to merge simple-card and simple-scu-card.

These sound cards are using silimar but not same logic on each functions.
Then, of course we want to share same logic.
To compromise, this patch uses cpu/codec pointer on simple-scu-card.
It is same logic with simple-card, thus easy merging.
This is prepare for merging simple card

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