ASoC: rsnd: use defined io_playback/io_capture

rdai->playback/rdai->capture are defined as io_playback/io_capture
on __rsnd_dai_probe(). Let's use it instead of original one.

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