ASoC: rsnd: tidyup ADG clock calculate method

Current ADG clock calculation needs ADG and SSI settings.
Thus, SSI side clock request function depends on ADG settings.
After reconsideration,  we can close this method inside ADG.
This function uses new method. And it becomes preparation for
AUDIO_CLKOUT support.

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