ASoC: rsnd: call rsnd_scu_ssi_mode_init() from SSI

Current R-Car sound driver is assuming that
SCU mod is used even though it is not needed.
Because scu.c is controlling SSIU too.
(it is Gen1 compatibility)
But, SCU mod will be really not used if new platform dai
feature was added.
Thus, rsnd_scu_ssi_mode_init() is called from SSI
directory by this patch.

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