ASoC: audio-graph-card: enable mclk-fs on codec node

Current audio-graph-card is supporting mclk-fs on CPU node
side only. But having Codec node also is good idea.
It will be just ignored if not defined.

"rcpu_ep" is same as "cpu_ep", This patch tidyup it, too.

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