ASoC: rsnd: add rsnd_get_adinr_chan()

Current rsnd driver has rsnd_get_adinr_bit() to get bit settings for
ADINR (= Audio Information Register) of SSIU/SRC/DVC.
This patch adds rsnd_get_adinr_chan() to get channel settings for
ADINR (= Audio Information Register) of CTU/MIX.

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>