ASoC: rsnd: add support graph base DT phase 1

To enable OF-graph base DT on rsnd driver, and to keep compatible
previous normal sound card style, it need to support both
"rcar_sound,dai" and "ports" (or "port") on DT.

This patch modify rsnd_dai_of_node() to parse
"rcar_sound,dai" and "ports" (or "port") as phase 1. It can detect
graph base style, but do nothing at this point.

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