ASoC: rsrc-card: use snd_soc_of_parse_audio_route/prefix for routing

using common audio routing path method makes sense.
Let's use snd_soc_of_parse_audio_route/prefix.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Tested-by: Keita Kobayashi <keita.kobayashi.ym@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>