ASoC: rsnd: add rsnd_io_to_mod()

Sometimes we would like to get each module directly, especially data path
searching. this patch adds rsnd_io_to_mod() macro, and existing
rsnd_io_to_mod_xxx() use it.

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>